[Y_Y]

Since you asked, my objection is both aesthetic and semantic, though I was really referring to the semantic part above.

I think you've hit the nail on the head with this visual vs. verbal distinction.

I can add a few clarifying details. I don't use IDEs as much as basic text editors maybe with highlighting, and I try not to rely on any fancy features. It does worry me that the allcaps use you describe is (afaik) not known to the editor or interpreter, so if you make a mistake or the symbol gets out of sync with its meaning (re: pattern variables) you may have a false signal. Finally I'll say that in the end I can't suggest a good way to treat these special variables, and so maybe I don't get it, or tastes like mine would be better served by a different formalism for macros.