Reply-spam is way more of an issue than I realised. If your federated timeline of your selfhosted server is public, like I think it is for PeerTube, any link spam replies to external videos just get hosted by you while on e.g. Wordpress these would have ended up in the moderation queue. At least I have disabled search engine indexing of external videos on my PeerTube, and made the federated timelines non-public on Friendica and Pleroma, so they don't get any seo satisfaction.