I think my request for a wildcard search would dovetail nicely with the solution to this problem. It would allow users to look up a song title and see what versions of it exist in the database. Not perfect, because someone could still play that extended live version of a song before realizing they were on the same scoreboard as folks who played the album version, but I'd at least be sure to check ahead of time for a live version/remix/alternate take of a song to see how others were tagging it.
I also think the suggestion was made somewhere to allow people to vote to merge or split songs when it became clear that two separate recordings were sharing a scoreboard. I appreciate that this would not be easy to implement. But maybe a good fix in the meantime would be to allow a player, immediately after playing a song, to correct the way that the song is listed. (This shouldn't be free-for-all - i.e. I can't score six digits on some 20-minute prog-metal epic and then try to pass it off as the latest Coldplay single. But maybe similar titles/spellings of the artist name could be suggested - sort of like the "Did you mean...?" when you misspell something in a Google search - and allow the player to move a score to that song when they realize they've got it in the wrong place. Sure, there's potential for abuse there, but no more than there already is when people intentionally tag their mp3 files in misleading ways.)
In the meantime, I try to re-tag to fit popular conventions where possible. Example: "Mutemath" without the space and "Mute Math" with the space both exist, with the same songs on separate scoreboards under each artist name. I'll tag accordingly so that I'm competing with whichever one has the highest score logged by another player thus far.