[Strom]

Classic scene groups are not interested in having their releases spreading on torrent sites, so including any signatures would be helping with what they don't want to happen in the first place.

That said, a third party could add a signature. But in practice a cryptographically secure signature isn't even needed. It boils down to a reputation system, so that you can associate a torrent file with quality and this has already existed since forever on sites like the piratebay in the form of uploader usernames. A lot of torrents are uploaded by the same users, users who have a history of quality torrents. In contrast, a hollywood uploader would never have any actual quality torrents in the account history. So in conclusion, this problem was already solved ages ago.