diff --git a/docs/developer/src/SUMMARY.md b/docs/developer/src/SUMMARY.md
index a18b0fe02e..6231f1d5fa 100644
--- a/docs/developer/src/SUMMARY.md
+++ b/docs/developer/src/SUMMARY.md
@@ -28,7 +28,7 @@
     - [ORM and Caching](./core/orm_and_caching.md)
     - [Interfaces](./core/interfaces.md)
     - [UI](./core/ui.md)
-    - [Internationalization](./core/i18n.md)
+    - [Internationalisation](./core/i18n.md)
     - [Utils](./core/util.md)
     - [Queues](./core/queues.md)
     - [Files](./core/files.md)
diff --git a/docs/developer/src/core.md b/docs/developer/src/core.md
index c557e71c98..88af5e6826 100644
--- a/docs/developer/src/core.md
+++ b/docs/developer/src/core.md
@@ -15,4 +15,5 @@ The `core` tries to be minimal. The essence of it being various wrappers around
 - [Queues](./core/queues.md);
 - [Files](./core/files.md);
 - [Sessions and Security](./core/security.md);
-- [HTTP Client](./core/http.md).
\ No newline at end of file
+- [HTTP Client](./core/http.md).
+- [Exceptions](./core/exception_handler.md).
\ No newline at end of file
diff --git a/docs/developer/src/i18n.md b/docs/developer/src/i18n.md
index 015d768f4b..3ba613ceed 100644
--- a/docs/developer/src/i18n.md
+++ b/docs/developer/src/i18n.md
@@ -1,14 +1,61 @@
-### Internationalization and localization
+Internationalisation
+====================
 
-For info on helping with translations, see the platform currently in use
-for translations: https://www.transifex.com/projects/p/gnu-social/
+Usage
+-----
 
-Translations use the gettext system <http://www.gnu.org/software/gettext/>.
-If you for some reason do not wish to sign up to the Transifex service,
-you can review the files in the "locale/" sub-directory of GNU social.
-Each plugin also has its own translation files.
+Basic usage is made by calling `App\Core\I18n\I18n::_m`, it works like this:
+```php
+// Both will return the string 'test string'
+_m('test string');
+_m('test {thing}', ['thing' => 'string']);
+```
 
-To get your own site to use all the translated languages, and you are
-tracking the git repo, you will need to install at least 'gettext' on
-your system and then run:
-    $ make translations
+This function also supports ICU format, you can refer to [ICU User Guide](https://unicode-org.github.io/icu/userguide/),
+for more details on how it works. Below you find some examples:
+```php
+$apples = [1 => '1 apple', '# apples'];
+
+_m($apples, ['count' => -42]); // -42 apples
+_m($apples, ['count' => 0]); // 0 apples
+_m($apples, ['count' => 1]); // 1 apple
+_m($apples, ['count' => 2]); // 2 apples
+_m($apples, ['count' => 42]); // 42 apples
+
+$apples = [0 => 'no apples', 1 => '1 apple', '# apples'];
+_m($apples, ['count' => 0]); // no apples
+_m($apples, ['count' => 1]); // 1 apple
+_m($apples, ['count' => 2]); // 2 apples
+_m($apples, ['count' => 42]); // 42 apples
+
+$pronouns = ['she' => 'her apple', 'he' => 'his apple', 'they' => 'their apple', 'someone\'s apple'];
+_m($pronouns, ['pronoun' => 'she']); // her apple
+_m($pronouns, ['pronoun' => 'he']); // his apple
+_m($pronouns, ['pronoun' => 'they']); // their apple
+_m($pronouns, ['pronoun' => 'unknown']); // someone's apple
+
+$complex = [
+    'she'   => [1 => 'her apple', 'her # apples'],
+    'he'    => [1 => 'his apple', 'his # apples'],
+    'their' => [1 => 'their apple', 'their # apples'],
+];
+
+_m($complex, ['pronoun' => 'she',  'count' => 1]); // her apple
+_m($complex, ['pronoun' => 'he',   'count' => 1]); // his apple
+_m($complex, ['pronoun' => 'she',  'count' => 2]); // her 2 apples
+_m($complex, ['pronoun' => 'he',   'count' => 2]); // his 2 apples
+_m($complex, ['pronoun' => 'she',  'count' => 42]); // her 42 apples
+_m($complex, ['pronoun' => 'they', 'count' => 1]); // their apple
+_m($complex, ['pronoun' => 'they', 'count' => 3]); // their 3 apples
+```
+
+Utilities
+---------
+
+Some common needs regarding user internationalisation are to know
+his language and whether it should be handled Right to left:
+
+```php
+$user_lang = $user->getLanguage();
+App\Core\I18n\I18n::isRtl($user_lang);
+```
diff --git a/src/Core/I18n/I18n.php b/src/Core/I18n/I18n.php
index 4b8af051b9..bee6ebce0d 100644
--- a/src/Core/I18n/I18n.php
+++ b/src/Core/I18n/I18n.php
@@ -36,7 +36,10 @@
 
 namespace App\Core\I18n;
 
+use App\Util\Common;
+use App\Util\Exception\ServerException;
 use App\Util\Formatting;
+use Exception;
 use Symfony\Component\Translation\Exception\InvalidArgumentException;
 use Symfony\Contracts\Translation\TranslatorInterface;
 
@@ -70,6 +73,10 @@ abstract class I18n
      * Looks for which plugin we've been called from to get the gettext domain;
      * if not in a plugin subdirectory, we'll use the default 'core+intl-icu'.
      *
+     * @param string $path
+     *
+     * @throws ServerException
+     *
      * @return string
      */
     public static function _mdomain(string $path): string
@@ -105,7 +112,7 @@ abstract class I18n
         $all_languages = Common::config('site', 'languages');
 
         preg_match_all('"(((\S\S)-?(\S\S)?)(;q=([0-9.]+))?)\s*(,\s*|$)"',
-                       strtolower($http_accept_lang_header), $http_langs);
+            strtolower($http_accept_lang_header), $http_langs);
 
         for ($i = 0; $i < count($http_langs); ++$i) {
             if (!empty($http_langs[2][$i])) {
@@ -256,7 +263,7 @@ abstract class I18n
                 $pref = '';
                 $op   = 'select';
             } else {
-                throw new Exception('Invalid variable type. (int|string) only');
+                throw new ServerException('Invalid variable type. (int|string) only');
             }
 
             $res = "{$var}, {$op}, ";
@@ -298,7 +305,9 @@ abstract class I18n
  *    _m(string|string[] $msg, array $params)              -- message
  *    _m(string $ctx, string|string[] $msg, array $params) -- combination of the previous two
  *
- * @throws InvalidArgumentException
+ * @param mixed ...$args
+ *
+ * @throws ServerException
  *
  * @return string
  *
@@ -307,33 +316,33 @@ abstract class I18n
 function _m(...$args): string
 {
     // Get the file where this function was called from, reducing the
-    // memory and performance inpact by not returning the arguments,
+    // memory and performance impact by not returning the arguments,
     // and only 2 frames (this and previous)
     $domain = I18n::_mdomain(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS)[0]['file'], 2);
     switch (count($args)) {
-    case 1:
-        // Empty parameters, simple message
-        return I18n::$translator->trans($args[0], [], $domain);
-    case 3:
-        if (is_int($args[2])) {
-            throw new Exception('Calling `_m()` with an explicit number is deprecated, ' .
-                                'use an explicit parameter');
-        }
+        case 1:
+            // Empty parameters, simple message
+            return I18n::$translator->trans($args[0], [], $domain);
+        case 3:
+            if (is_int($args[2])) {
+                throw new Exception('Calling `_m()` with an explicit number is deprecated, ' .
+                    'use an explicit parameter');
+            }
         // Falthrough
         // no break
-    case 2:
-        if (is_array($args[0])) {
-            $args[0] = I18n::formatICU($args[0], $args[1]);
-        }
+        case 2:
+            if (is_array($args[0])) {
+                $args[0] = I18n::formatICU($args[0], $args[1]);
+            }
 
-        if (is_string($args[0])) {
-            $msg    = $args[0];
-            $params = $args[1] ?? [];
-            return I18n::$translator->trans($msg, $params, $domain);
-        }
+            if (is_string($args[0])) {
+                $msg    = $args[0];
+                $params = $args[1] ?? [];
+                return I18n::$translator->trans($msg, $params, $domain);
+            }
         // Fallthrough
         // no break
-    default:
-        throw new InvalidArgumentException('Bad parameters to `_m()`');
+        default:
+            throw new InvalidArgumentException('Bad parameters to `_m()`');
     }
 }
diff --git a/src/Core/I18n/TransExtractor.php b/src/Core/I18n/TransExtractor.php
index 8928df6a73..ae74e249c3 100644
--- a/src/Core/I18n/TransExtractor.php
+++ b/src/Core/I18n/TransExtractor.php
@@ -35,10 +35,13 @@
 namespace App\Core\I18n;
 
 use App\Util\Formatting;
+use ArrayIterator;
+use function count;
+use InvalidArgumentException;
+use Iterator;
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\Translation\Extractor\AbstractFileExtractor;
 use Symfony\Component\Translation\Extractor\ExtractorInterface;
-use Symfony\Component\Translation\Extractor\PhpExtractor;
 use Symfony\Component\Translation\Extractor\PhpStringTokenParser;
 use Symfony\Component\Translation\MessageCatalogue;
 
@@ -135,7 +138,7 @@ class TransExtractor extends AbstractFileExtractor implements ExtractorInterface
     /**
      * Seeks to a non-whitespace token.
      */
-    private function seekToNextRelevantToken(\Iterator $tokenIterator)
+    private function seekToNextRelevantToken(Iterator $tokenIterator)
     {
         for (; $tokenIterator->valid(); $tokenIterator->next()) {
             $t = $tokenIterator->current();
@@ -148,7 +151,7 @@ class TransExtractor extends AbstractFileExtractor implements ExtractorInterface
     /**
      * {@inheritdoc}
      */
-    private function skipMethodArgument(\Iterator $tokenIterator)
+    private function skipMethodArgument(Iterator $tokenIterator)
     {
         $openBraces = 0;
 
@@ -170,10 +173,11 @@ class TransExtractor extends AbstractFileExtractor implements ExtractorInterface
     }
 
     /**
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      *
      * @return bool
      *
+     *
      */
     protected function canBeExtracted(string $file)
     {
@@ -195,7 +199,7 @@ class TransExtractor extends AbstractFileExtractor implements ExtractorInterface
      * Extracts the message from the iterator while the tokens
      * match allowed message tokens.
      */
-    private function getValue(\Iterator $tokenIterator)
+    private function getValue(Iterator $tokenIterator)
     {
         $message  = '';
         $docToken = '';
@@ -245,7 +249,7 @@ class TransExtractor extends AbstractFileExtractor implements ExtractorInterface
      */
     protected function parseTokens(array $tokens, MessageCatalogue $catalog, string $filename)
     {
-        $tokenIterator = new \ArrayIterator($tokens);
+        $tokenIterator = new ArrayIterator($tokens);
 
         for ($key = 0; $key < $tokenIterator->count(); ++$key) {
             foreach ($this->sequences as $sequence) {
@@ -262,7 +266,7 @@ class TransExtractor extends AbstractFileExtractor implements ExtractorInterface
                     } elseif (self::MESSAGE_TOKEN === $item) {
                         $message = $this->getValue($tokenIterator);
 
-                        if (\count($sequence) === ($sequenceKey + 1)) {
+                        if (count($sequence) === ($sequenceKey + 1)) {
                             break;
                         }
                     } elseif (self::METHOD_ARGUMENTS_TOKEN === $item) {