An alternative for Post Kinds (and my—even simpler than Shortnotes—https://github.com/janboddez/indieweb-custom-post-types)?
Think the one thing I do differently is not store anything in custom fields. Reply-to or bookmark URLs are simply part of the post content and easily parsed out. (I manually add `u-*` classes to links. Win some, lose some, I guess.)
(Not even manually, in fact, when I use on Indigenous + Micropub.)
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