I think Talkyard does what you have in mind: https://www.talkyard.io — it's both community/forum software, and blog comments: https://www.talkyard.io/blog-comments, and the blog comments are placed in a blog-post-discussions category in the forum. The same login & @username_mentions work both in the blog comments and in the forum. (I'm developing Talkyard & it's open source beta software.)
I'm looking to create a PWA mobile app, meaning, people will get one's community as its own icon on their mobile phone.
