I think webmentions would be the answer there, though I don't think Bluesky currently supports it so you'd be looking at scraping rather than a push-based model.
you can just post a message on bluesky and link it to your blog post at the end with some text saying "want to comment? Reply to this post."
Personally, I prefer using webmentions. I got them back to my site using a combination of services, so if someone talk about a post I made in bluesky or mastodon, I usually get a webmention back to the post.
I guess it could just be done as a multi phase post, as janky as that is.