Certain communities are continuations of those that are/were on Reddit. The "post link to a paywalled article, everyone bitches about the headline" section of the world is a carbon copy. A lot of the technical space...I haven't encountered as many "May God create a deeper, hotter hell for you and your family if you buy Intel over AMD" types here, though this may have been because I haven't really found a substantial PC hardware community.
Commercial Republicanism doesn't seem to be anywhere near as present. The folks with a mossy oak jacket instead of a personality...there's a few of them here but the extremists actually seem to be Stalinites.
The various permutations of No Stupid Questions or Ask Lemmy aren't as dick-in-hand horny as Reddit's were (I'm guessing there's fewer teenagers here), though there's a lot more talk about the platform itself. slow turn to look at OP
Official discussion boards are completely absent. Nobody's ending Youtube videos with "Go check out our Lemmy community." I'll use the example of Coffee Stain Studios' game Satisfactory: Snut still occasionally mentions their subreddit, and while there is a community here, it's A. unofficial and B. almost entirely dead.
The brain trust feels gone. Stuff like r/tipofmytongue or r/whatisthisthing or r/askhistorians just hasn't happened here yet, possibly because of the lower population. I'm less confident that I can get an actual answer to "What's this weird piece of bent metal I found in the back of my grandmother's silverware drawer for?" or "What's that movie where a guy pulls a nuclear bomb with an ATV and gets radiation sickness?" I don't foresee AMA's or anything like that, though it seems that was dying off on Reddit as well.
Moderators overall seem to be doing an amazing job, because the place seems well moderated, I don't really notice the mods doing their jobs as much (possibly because Lemmy doesn't do the deleted by moderator thing that Reddit did for some reason), and I've yet to see or hear about a mod being a human case of pink eye like you'd see so often on Reddit. Use Reddit for awhile and you build up a list of moderator names and the subs they ruin, the same list on Lemmy is still blank so far.
It's still the internet, which means The Worthless are present and accounted for. You know, the "people" who didn't get enough attention as children who exist only to make casual conversation via text impossible via interpreting every sentence as 100% true and literal. Say something like "Raiders of the Lost Ark was better than Last Crusade" and The Worthless are guaranteed to show up and try to lecture you about opinion versus objective fact.