The other xwidget authors are properly posting to "Customization / Skins & Themes / Windows Utilities / Applications" which is where this belongs. Not only are you just confusing and wasting the time of Rainmeter users, you are making it harder for xwidget users to find your deviations. You are doing nobody any favors by continuing to ignore how deviantART works. It doesn't help your users or ours.
I agree with your cause, but you definitely could have been kinder about it. Maybe the author was confused and needed some kind advice. If you wanted to be this rude, I believe a comment like this (which doesn't even say anything about the deviation) is better suited as a note.
I actually was a lot kinder the first time this user improperly posted a false .rmskin here. I'm not trying to beat the guy up, he means well. However, there is a place ("Customization / Skins & Themes / Windows Utilities / Applications") that the other xwidget authors have gravitated to until an xwidget area can be set up by DA, and I am fearful of causing a lot of confusion for both Rainmter and xwidget users if this behavior of creating a completely invalid .rmskin that can only blow up with an error dialog becomes a habit.