(How) Does Lemmy prevent brigading and other vote manipulation?
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.
Malicious instances would need to be blocked by the instance you are registered to.
Couldn't they keep the instance running and just change the domain name? Or if not easily possible, then just have a setup script that creates a new instance under the new domain name with X number of users.
As for multiple accounts - couldn't the same thing be done on reddit? Just make a bunch of alts and self-inflate your own posts/comments.
Sure, but as mentioned it might be easier with Lemmy since they could just run their own instance. Or maybe it's harder because Lemmy admins check account creation better on their own instance and are more sceptical of other instances.
It's an interesting topic, time will tell how it's gonna be. It certainly isn't bad to talk about it already today. ;)