Been on Reddit since 2010. I'm hoping that Lemmy and other Fediverse apps sort of grow out of the meta-talk and comparisons to their centralized counterparts.
Otherwise, the communities themselves seem pleasant (or swiftly defederated from by the good ones). We don't quite the critical mass to get active niche communities, or hyper-specialized ones yet, which I kind of miss. Stuff like "here's a subreddit for each of these very specific habits that cats can have", or "talk about a particular species of parrot", y'know?
It'll happen if Lemmy gets big enough. I only worry about search engines getting tangled in the natural duplication of Lemmy posts.
Like, if a web crawler sees a Beehaw post, and then seees Lemmy.ml's mirrored page of that same post, could it just show up as two different results? Could it work against the SEO in that it gets marked as "duplicate" or "spam" content in some way?