Whoa, awesome discussion in your webmentions!! Really appreciate the thought-provoking ideas and proposal. For the publish-to-Facebook cases, geez it does kind of feel like the only alternative if we want absolutely everything captured. It’s not a big itch for me — I like/comment on Facebook pretty rarely, and since 95% of my friends post everything friends-only anyway, I’m mostly not comfortable posting those interactions on my site at all.
For the quick tweet replies and likes, where it’s still technically possible to do through the API, I’m not ready to throw in the UX towel yet! (FWIW I’m hacking on a little indieweb reader, I expect it will always be crude and never up to Shrewdness quality but it will most definitely be able to send a micropub like with one click)