Perhaps I'm getting ahead of everyone, as this appears to be a new feature and this may already be planned. But in case it isn't, I shall request it.
If you frequent a tag very often, it appears that if it is not a part of a tag set of yours, or part of your favorite tags, it will get set as a "frequented tag", that is highlighted.
It sprung up on me in the middle of my browsing... one second, I had a page of white questions, and then on refresh a great fraction turned blue. On the right, it says "set tag preferences", but there's nothing I can set to actually affect this, because I have no tag preferences.
Could we enable a preference setting to turn this feature off? I can understand abiding by the rules of highlighting when I actually set favorite tags. It could also be a means to educate users as to the existence of the tag preference system, if they have not yet known about it. But for users who do know it and willingly decide not to use it, could we have the ability to choose not to have this highlighting?