Nice bit of reconstruction, and that you're factoring at the indieweb protocol level makes sense. Another protocol you may want to look at is WebSub so you don't need to poll your feeds so often, but can call web hooks when they are updated.
Perhaps you could put it inside a details/summary block, so the info is there if they want to expand it?
That leaves the option of revealing it in a sidebar on larger screens, for example.
Nice summary of h-card and structure, but why hide it from site visitors? Surely it's interesting for them too.
That's why we have webmention.rocks to help you test them
Yes: I'll be indoors this time
Interesting approach to caching partial pages with service workers - I wonder if this would extend to a feed of notes well with a list of partials?
Nice to see you adding webmentions