Actually, I just realized that my main gripe with this tag is a gripe that I have with dress tagging in general.
The majority of the posts that were the first ones that used jacket over dress were of Hiyajou Maho (despite how she is wearing a cardigan and not a jacket), and a good chunk of these posts didn't feature her lower half at all. Even though I'm personally under the impression that you should still tag what you see and not what you know, even in regards to a character's costume, I don't care how people tag dress. They're gonna tag dresses even if it's a portrait, even if it's impossible to tell that character is wearing a dress without already knowing in your mind that the character is wearing a dress in their full costume, I don't care.
What bothers me so much about this tag just seeing how it was created is that, if it is allowed to exist, it is going to be another tag that is populated with people tagging what they know and not what they see. Contrast that with tags like jacket over swimsuit and jacket over hoodie where people do not tag those when it is not apparent that the character is wearing a hoodie or that the character is wearing a swimsuit. That's what my gripe is with this tag. To me, that uncertainty is what makes it padding.
Does that make any sense?