Also I may switch to kbin because it seems like it is more friendly with lemmy instances, than lemmy is with kbin instances. I wish there were more instance providers for it though. kbin.social is slow.
I think they mean other fediverse clients, like any mastodon instance, any calckey instance, etc. (not sure if there are more that work currently). It will just show communities as an account where all the posts in the "subreddit" look like tweets and the comments are replies. It's pretty neat and gives us a glimpse of a world where you can comment on a reddit post / reply to a comment from a twitter account/ui.