Cross-site replies.
When replying to a post, Micro.blog will attempt to send a Webmention to that post. This allows the other site to include the reply alongside the original post.
Hosted blogs on Micro.blog can also receive Webmentions from other sites outside of Micro.blog. If the site URL has been verified in a Micro.blog user’s profile, Micro.blog can also match the incoming Webmention with a Micro.blog user and use their username. If not, Micro.blog will create a special “domain name” user for the incoming Webmention.
Micro.blog assumes 1 user = 1 blog. Multi-user services like Brid.gy which forward social networks via Webmention do not always work with Micro.blog because the social network users all share a single domain name. Micro.blog has special support for Mastodon and Bluesky webmentions via Bridgy.
To show Micro.blog replies (including Webmentions) on your Micro.blog-hosted blog, you can enable Conversation.js.
To use Micro.blog to keep track of webmentions sent to an external site, see this page on Micro.blog.
See this help page for more about how replies are processed on Micro.blog.