I'm not sure when the tag-popup changed, but when activated by mouse-over, the button color is a bit over-bright for the dark theme and the rest of the text in the popup. For example,
As a suggestion, it looks like if the button (highlight behind "Watch tag") was reduced to just occupy the center 1/3 of the dialog, the same attention grabbing effect could be achieved without the full-width (or 90% or whatever it is) that draws the eyes away from the rest of the text. I do see the intent to be to have a consistent margin/padding for the dialog text and button, so another option may be to tone down the highlight color.
This isn't to say the way it is is bad or wrong or looks bad, just the highlight seems to overpower the remaining text in the dialog. It caught my attention, as it usually does by accidental mouse-over, so I thought I would pass it along for discussion. It certainly isn't any type of major issue.