Flag deleted TVDB shows
Trakt relies a lot on TVDB for shows. Sometimes TVDB has duplicates which eventually get fixed. But when that happens, these dupes are still available on Trakt.
I suggest coming up with a notification system that warns when a show has a TVDB entry disappear. Who would get notified? Well, mostly you guys, since you're the ones with the ability to remove dupes. Maybe you could also add a warning on the show page that the TVDB entry is gone and that Trakt admins are investigating.
This might cut down on dupes and the constant reports about them.
Note: this implies that shows on Trakt auto-refresh periodically, otherwise the disappearance of a TVDB entry will never be noticed. I assume that is the case.
I've recently requested removal of duplicate shows 5 different times on Trakt. I know it's not your fault: TVDB has dupes, and you end up getting those. I also try to report them to TVDB when I find them, then to you when TVDB takes care of them.
However, this is becoming repetitive. I really do think you need to create a system that automatically flags those shows on your end when they disappear from TVDB.
I don't know if you just want to notify yourselves/users when that happen, or simply purge the data, but this automation is needed at this point.