Femcel is indeed usually the same as incel, but with vaginas. But there's always mudiness around slang terms, even more than formalized terms.
Also, there is a standard for lemmy. They're communities, or (for the lazy like me, C/s), it's just that reddit exodus people tend to be too lazy to use the standard term.
There's a reason that every community url includes the c/ as part of it. That's how standardized it is, it's in the basic underpinning of lemmy. The choice of c/ wasn't arbitrary. Well, that's what one of the devs said (though not as a quote, I'm paraphrasing) back last year (iirc, could have been before that, I did lurk some on lemmy before the reddit fiasco).
Magazine was used guy kbin, and then mbin, which are similar federated platforms.
We all understand communities, it's only the folks that haven't caught up yet, or haven't paid attention that don't understand.