I'm listing this both as a bug and a feature request since it's subjective as to which it might be.
I discovered while discussing another feature request that I can mark a tag as both Ignored and Interesting. This leads to question lists that look like this:
Now, perhaps this is intended behavior, but it seems counter-intuitive to me. I would argue that it would be best to make ignore / interesting mutually exclusive. If you try to add one and it's on the other list, you get the Red Popup of DOOM telling you to remove it from the other list first.
Edit: Well, I have my answer: it's by design. I can live with that. Just seems counter-intuitive, is all.