The trackers only deal with torrents' info hash. No names, no descriptions, no list of contents, no nothing. opentracker, to use OP's chosen software as example, can run in both white- and blacklist mode (or whatever equivalent terminology it uses today). The former is self-explanatory, and the latter allows all hashes except the blacklisted ones. All open trackers, such as torrent.eu and opentrackr.org to name a couple, always operate in a blacklist fashion in order to openly accommodate any users to congregate for (almost) any content.