Looking at the account on toast.ooo, https://toast.ooo/u/NoMoreTrds, it seems that the home instance ban may not have removed all content, that's something @grant@toast.ooo should be able to fix by banning the user again with content removal selected.
if they've posted or commented in the community, visit the post/comment and it'll be in the menu, same place where you'd be able to report/remove/etc.
if they haven't posted or commented, it's not possible in the default lemmy ui, but you can use e.g. tesseract or photon to do so in the community settings.
of all the scrapers we see, the requests identified as originating from Meta seem to be well behaved overall. they appear to (mostly) be respecting robots.txt where present and their request volume to Lemmy.World is only averaging slightly above 5 requests per minute over the last 2 weeks. they also don't spoof their user agents to pretend to be web browsers, or at least I have not seen credible accusations of this happening.
based on your other post, which has since been removed by moderators of that community, it seems that you are looking for the !perchance@lemmy.world community instead of this one.
you're not going to have much luck here, as here people won't even understand what you're talking about.
please remove the phishing link from this post immediately. you can defuse it e.g. by putting it in a code snippet and replacing the dots with [.], e.g. netprocesse[.]com.
lemmy currently doesn't have granular federation controls. the only option right now is to defederate from mbin instances, but other instances might still announce your users' votes to mbin instances. the more hacky way would be to also block federation related http requests from mbin instances to prevent them from retrieving user profiles, which is probably the most effective method that could be used.
piefeds non-federated votes are a user setting for the default value and users have the option for each vote whether it should be federated. see also https://piefed.social/post/982478
as explained in this post, the original implementation of "private voting" has already been replaced with non-federated voting, which addresses the abuse concerns, as it's then limited to just the instance the votes are cast on.
piefed is a fair bit younger, the first commitin the git repo was on Fri Jul 28 02:07:44 2023 +0000. it has only in recent months started really picking up some traction with several lemmy instances already creating piefed instances as well.
lemmy doesn't support subscribing to users, but you can subscribe to communities the same way you'd subscribe to other communities from other instances.
that's not a thing on lemmy. it's probably just the user setting to hide bot accounts.