People posting whatever they want wherever they want and having very little understanding of nuance in language I dont think this would be a huge problem, mods can remove unwanted content and instances can decide what type of users they want to accept. As for misusing downvotes I think that issue never has ever mattered and the difference between reddit and lemmy is we have a open source algorithm to decide how content is served. If anyone can think of a better way to server content they're free to put that in.

moderators becoming more power hungry This is an issue on every platform but Lemmy is more insulated against it than reddit for two reasons. First is that we can have the same community name shared across servers. On reddit once someone gets the catchy community name they can camp it forever. On Lemmy you can just make the community somewhere else with the same name. Second, each instance can decide how it wants to moderate its communities on Lemmy ML they are OK with power hungry mods but on other instances its frowned upon. On reddit its ignored completely.

One thing that makes Lemmy better is that its made by the users for the users. We have the code, we have the protocol its built on. This means we can have Lemmy tailored to however we want. We are not at the whim of a massive company that only cares about profit. If I have an idea for a feature i can goto the github and suggest it, better yet if I could program it I could help build that feature. If I dont like a change that is made by the lemmy devs I can fork the project and remove the change and still interact with the rest of lemmy.