Yeah I can see this being an issue with the fediverse in general. There really is no ability to completely block someone or remove them from the fediverse. Some see this as a benefit, some see this as an issue.

Lemmy allows other instances by default, so nothing stops a bad actor from just spamming instances on subdomains to harass or spam. I just hope we don’t end up with a system where instances are defederated by default because then that will seriously fragment the community.