I like all my categories to be structured pretty, and with nicely formatted words. I like my tags to be quick and all lowercase. After spending too much time fighting WordPress for duplicate slugs (e.g. multiple “PHP” categories and a “php” tag) I gave up on that. I decided to let WordPress have its category and tag both be the same “term”. The problem now is that all my tags looked nice except for a few, which were uppercased matching the category names they conflicted with.
After a little bit of filter debauchery, I crafted up this simple enough solution.