Not to say that I've never done it, but I don't use them for negative things very often. I just like to remind myself of things. For example, I've started a few Lemmy friendships that then moved to one messenger or another; I have those users tagged with their first names so I'm sure to notice when a post is by a friend.

Or, back when I used Connect, I had quite a few tags; a lot of them were because a user said something interesting about themselves of which I wanted to make note. One that comes to mind - though I'm not sure if this person is still around - was a user who said "I'm just a construction worker with a camera" so I tagged them as such.