You’re right, and yet this is probably the one thing that frustrates me about micro.blog the most: micro.blog does everything it can to drag you in. You can’t reply to a micro.blog post from your own site without being registered at micro.blog. You don’t receive webmentions on your site from the conversations you participate in on micro.blog. Instead of being a good IndieWeb citizen, micro.blog actively tries to be the center, the single point to concentrate your social interactions, and, admittedly, is quite good at it.
Comments are webmentions.