Ah so I gather the current situation is that translation_request means that a post should be translated for the community's sake, not necessarily that any given user wants to read it. Without an easy outlet for an individual to express beyond what the tag already does, people will use what's in front of them and comment. This leads translation bumps to be a common comment that would be impractical to explicitly ban and therefore persist until eternity.
I mean I don't want to encourage it by translating after a TL bump but I also wouldn't want to leave a partially translated pool untranslated that someone wanted to read recently...
A way to watch posts for translation would be nice. Assuming that most of the user favorite functionality is recyclable then maybe it could be done but then again real life always kicks plans in the face.