Unidan could just create an account on multiple instances and vote for his posts/comments with all these accounts. That way his content would gain more attention than those of sincere users.
In case of malicious bots (like those annoying bootleg bots on reddit), it might even be profitable for them to create their own instance(s) just for that purpose.
Is there a mechanism to prevent that? (other than user/instance banning and the introduction question on user creation)
There isn’t and Lemmygrad.ml users have been doing it in the past. Mostly down-vote brigading though and this is the main reason why down-votes are disabled on our instance.
Personally I think there should be a setting to prevent down-votes from federating as there is really no point in federating them to instances with other rules and different community culture.
Huh - I had not even considered downvotes in other instances… Yeah that seems problematic. Maybe rather than defederating downvotes, there could be a way to differentiate between local and global up/downvotes.
Brigaded up-votes are almost as harmful as brigaded down=votes. Down-votes also keep out the trolls until a critical mass of trolls has been reached. Hopefully there are more advanced methods in the future.