[esjeon]

> all the notifications in a mismatch of languages showing up in the main feed

I'm not quite expert here, but, IIRC, this language problem is partially inherent to ActivityPub. The sender can attach translations, and the receiver can pick one from the set, but no one knows what's gonna happen if the expectations from both sides don't match.

One might, instead, re-fetch the messages from the sender using HTTP + content negotiation, which will definitely cause different types of headache.