‘Lemmitor’ is too much like ‘Redditor’.

Lemmitor is used derogatively, the point is precisely to highlight how a bunch of users left reddit but try to shape Lemmy into exactly the sort of place they left (or were kicked out of) starting with its worst aspects. It's mostly used to describe a user who engages in annoying redditisms such as that obnoxious John Oliver kind of shallow, terminally ironic outlook on politics.

Yes, that's the joke.