The only instance I’ve blocked is feddit.online, because it’s a pure reddit mirror with no users or fediverse-native posts. I found it clogged up my feed and made lemmy feel dead since there were all these posts with zero engagement, so I haven’t missed it at all and def recommend blocking it if your instance federates with it

Blocking an instance blocks the communities, not the users.

So I have .ml instance blocked, no post to a .ml hosted community will ever show up to my feed.

But if an .ml makes a post somewhere else, I see it.

I see their comments, and replies.

I just don't stumble into a place with authorarian moderation policies.