User blog comment:Fingersoop/Someone linked me to an illegal Vocaloid download host/@comment-32500188-20140526024921

Wow, that was silly of them to post a link to pirated software publicly like that... wonder why they thought that would be the best idea to prove their point when it could very well backfire and end up affecting their YT account status. v(=-=)v

I'd say you could delete the whole conversation and pretend it never happened/explaining why you removed their post from your video comments (which would save the user from getting strikes against their account for doing that if it was just a slip-up)... or if they decide to go and repost the link again, then go ahead and report their post. Either way, pretty sure it doesn't take much time for someone to catch wind of that and report the files to the hosting service once it gets revealed like that. :-P