Description
Reasoning is well explained here:
qbittorrent/qBittorrent#7965 (comment)
Private trackers that use this often fill in a three letter code specific for their tracker. Users that upload torrents can add it themselves (using dottorrent-gui for example) or the tracker will add it and the uploader needs to download the torrent with added tag from the tracker to start the seeding. Often people use different a locations for uploads than the default download location. So they will have to move files or edit download location and do a force recheck. If it would be implemented in the normal torrent creation process it would be much easier especially for novice users.
If if was not clear this is done to be able to cross-seed the same content between different private trackers. If no difference is made between the torrents the tracker addresses of the 2nd torrent will be added to the first and the seeders of both trackers will be mixed by the client.
For example, mktorrent can do this (pobrn/mktorrent@905ccc2) and thus often being recommended on such trackers as CLI .torrent creator.
Would be nice to see this in maketorrent as well. Thanks!