Lemmy has little links (like these: ) that connect every comment and post to their source in a user-friendly method. That makes a comment thread look similar to a link farm. Lemmy isn't alone in this, other Fediverse tools do the same.

Yeah, and that's what the canonical tags address: "hey I'm just a copy, my original location is Y". It's properly attributing the source of the data and should make search engines not mark it as duplicate content as a result. There's also tags to mark links as nofollow for indexing that should help with not looking like link farms either.

That should also mean only local content will count as content so that brings its own set of problems where small instances will never rank along the bigger ones.