Small shounen sites and female webmasters use them rather often. Nearly all of them are from your standard anime graphic and web layout resource site. They’re also known as Hentai Free Badges and there’s also an occasional yaoi one. Huge gap between the whole boy love fan and the fanservice junky. Notice the words yaoi fangirl weren’t used.

Image by Blissful Memoirs
This trend isn’t going anywhere fast, it’s pretty much dead. Active anime design sites aren’t paying such graphics any attention. Download, stream, forum, and other big anime themed sites have neglected this. People new to anime, young, or not into such anime and manga would take comfort in a site making it clear that they don’t allow it. If you don’t have such content, find space for a badge.