Well, it's that, our notes now have a language attribute.
... All right, all right, it's not just it.
First, the user panel section where the desired preferences are selected:
Upon sending the previous form, the user is redirected to order their selection:
Finally, when posting the language with the highest priority is selected by default.
However, by accessing "Additional options", another language may be selected. The resulting note will have the lang attribute according to it.
The posting widget itself:
We can now show you the notes you can read, but for groups, this mean that you can access umbrella groups and filter the feeds to see what's in your language and even region.
For too long the fediverse struggled with languages, this step makes it easier for actual internationalization of the free network.