Apologies if this has already been reported. I looked for and didn't find it, but may have simply missed it.

When you use smart add and type # and the beginning of a tag name you get a bunch of autocompletion possibilities. Very good.

Now go and delete a tag. I correctly gets deleted from all the tasks that had it. But it still shows up as a possible autocompletion possibility. There doesn't seem to be anyway to make it go away, which can be pretty darn annoying if you've got one that was a one-time typo!