I realize this is old, but couldn’t find another topic that was quite as on-point (I’m the Pat referenced in the OP).
We are starting to use pixls.us as a commenting platform for other libre graphics projects, and this problem is rearing its head again. Is there no way to specify more than one RSS feed to poll for posts still?
I love that I can at least specify multi-site embeds, but pointing to an RSS feed would be preferable to attempting to parse the html of the pages.