So here's how I think I can merge Mastodon and Commento:
Mastodon posts are HTML. So I need to do a LITTLE stripping (removing, say, @ mention links), but I can drop your text straight in, user name is, say "Teknikal_Domain (from the Fediverse)" and that's a link to your account profile. Comment text would also probably have a link to the original post at the bottom of it.
Favorites become Commento votes. Only public posts get counted. And I MIGHT be able to make CWs work as well.
The IDEA is that @tekdmn_blog will be watching my RSS and tooting out the summary, a link, and some hashtags. Anything it says it'll check every ~5 minutes to see who's replied, and start meddling with the Commento database. So I can't do it bidirectionally, but I think it's good enough.