This is related to the issue that was resolved here: https://getmusicbee.com/forum/index.php?topic=15050.msg98477#msg98477
I realized recently that MusicBee sorts and searches different quote and dash characters differently. Even if I don't have either character in Ignore Words, "I’m" sorts before If, and "I'm" sorts after If (as though the apostrophe weren't there). And I do want both of them in Ignore Words. It also won't find them both on a middle-click/library filter search.
A side note: when there are mixed titles, there's no drop-down on the title field where you can see them all.