Two things:

First, don't assume that just because you've never heard a word, that means no one has heard of it. There are quite a lot of us who know what the fediverse is.

Second, and this is a little pedantic, fediverse is a portmanteau, not an acronym.

Fediverse isn't an acronym, nor is it a term "no one's heard of". You haven't heard it before, and it's great to explain it, but don't project that either.

IMO It would be worse to editorialise the submission title

I've seen fediverse numerous times on HN