@indigo There isn’t, but there could be.
The point is not that it uses RSS but that the html contains machine-readable markup called microformats. This tells capable apps who the author is, what kind of post it is (reply, favourite etc), what the content is, if there is a photo, etc etc. Webmentions send the post and its metadata out and the receiving app then decides what to do with it, how to display and so on.
Webmention and mucroformats are the crucial elements. RSS is just one possible channel.
/@matigo @nitinkhanna