@JohnPhilpin Yep, that is correct, Micro.blog does not notify @-mentions for long posts. I've discussed this with @manton in the past and he had some concerns. For example: people creating very long posts, mentioning many people, as a way to get their spam out.
Regarding social timelines (on Micro.blog, Mastodon, Bluesky, etc.) and blog comments… I know Micro.blog kind of blurs the line between them, but I think they are quite different beasts. Commentary on social timelines are more ephemeral, and you have little to no control over what other people say about your blog there. A more traditional commenting system on your blog is more permanent, tied to the post, and you're 100% in control. Don't like a comment for whatever reason? Just delete it.
Say, for example, you had a WordPress blog set up to cross-post to Mastodon. One day, you decide to import 381 old posts from 2016. Mastodon doesn't have a concept of importing old posts to the timeline. So if someone would like to have a discussion on Mastodon about one of your old posts, they would have to create a new entry on their timeline, linking to your post.
In theory, you could ask your WordPress blog to cross-post all the 381 old posts to Mastodon during import as new posts, just to get entry-points for commentary. But your followers probably wouldn't like that very much. Your posts would take over their timelines. 😊 The same is true for a Micro.blog hosted blog and the Micro.blog social timeline.
All this to say, if you want a more traditional commenting system on your blog, you could hook it up to Commento or a similar service.