I think the limitations you mention with Webmention on Micro.blog — or having accounts — are temporary. I plan to expand both of those.
Oh definitely! I apologize if I’m coming across as critical - I’m kind of working in the dark here as to how one should connect with micro.blog from the outside. (How to craft replies, where Webmentions show up.) But this isn’t unusual—every blog has its quirks, its templates and conventions. There are a jillion microformats and there are Salmentions and so on. Anyway, on the contrary, I’ve enjoyed sorting out how to participate here and hope I can perhaps provide some useful stuff to you.