the rules depend on your instance. the admin on dbzer0 (this instance we're chatting on) said no direct links to pirated stuff, but suggested starting up other instances to federate with that would host it instead.
I imagine most lemmy instances would ban overt piracy.
we can talk about it and you can tell people about the mega thread or the name/top url of a site.
I think other boards on DB0 can also have torrent magnets.
I think it depends on the policies of the target instance and maybe your home instance too. Depends on if they want to risk the legal issues or not I guess.