I did some explorations a while back because a few people complained when I went from posting to my site a few times a month to posting sometimes 20-60 times a day for every tiny little thing.
Aside: I just looked and my site is putting out almost 10,000 posts a year, so maybe I need something more severe sounding than firehose? :O
You may have run across it in some of your research, but I’ve written a few tidbits that might help you refine some bits as you tinker. I’ll look forward to seeing what else your site does that mine can copy as well.
One thing I’ve been wanting to do as well is to provide some SubToMe buttons to help make it easier for people to subscribe to feeds from my site on my subscribe page. Perhaps that’s better than the page of crazy code people get when they click on RSS feed pages, especially if they don’t know what to do with those links?
One day I’d love to create a dashboard of all the feeds my site offers as checkboxes or something to let people create their own custom feeds using and/or/not operators using WordPress’ built in feed URLs, but it seems like an awfully big project.
Since you’re on micro.blog as well, I’ll mention that the concatenation of feeds using the Post Kinds plugins also allows me more direct control of what I pipe into micro.blog. I’m currently using the following feed in my account settings to post to m.b.:
https://boffosocko.com/kind/article,note,photo,read,watch,listen,bookmark,favorite/feed/
For your reply tests, feel free to use this post as a test ground if you like. For sites that support Webmention, you should be able to reply to my post directly from the webmention/comment in the comments section of your original post. But you could also try to create a completely new post that is a reply to this one as well. Both should work.
If you use Twitter along with Brid.gy I’ve also found an interesting “secret” there for creating nested threading:
https://boffosocko.com/2018/07/02/threaded-conversations-between-wordpress-and-twitter/