@JTR@micro.blog I think I finally get it...
I can @ my new micro.blog account from fosstodon.org, and the comment will show up over there, on micro.blog.
The benefit of the "mastodon" account on micro.blog is that replies to that account should show directly on my blog.
Meanwhile, I can write whatever I want there, and it will show up here, on this account, since I turned on cross-posting.
It's built with the assumption that you use micro.blog as you central hub.