Not advocating for defederation, I’m just pointing out that blocking an instance isn’t going to achieve their goal.

Obviously defederation is too large scale. Ideally, there would be an option for people to block users from the instance when blocking an instance, or something like that.

This would avoid the exact scenario you mention because it would come down to the user level, so that troll would have to put in quite a bit more effort to get around that. Unfortunately, that’s not currently an option, along with some other features I’d love to see on Lemmy.

Again, I’m just pointing out that blocking an instance does not achieve their goal.