When you tag your post in several categories, something very quizzical happens.

The bottom of the post still says " _ hours ago by _______ in _______" where the last blank is a single tag.

It chooses a single tag out of the many tags you provide.

So my question is:

How does it choose the tag?

It would be useful to know so I can make it choose the tag that is the most relevant out of the bunch.