Ipfs address depends on the content, so it's going to stay the same. Not sure if that public gateway supports registered names, but if it does, there would be ipns in the url. (https://dweb-primer.ipfs.io/classical-web/lessons/public-gat...)

(Comments are loaded in by JavaScript, so they're not included)

Yes it's a permanent url.

No the comments are not static: for this article they are served via disqus.

Aren't they served by Gitalk? There's a username dropdown, and inside there's a link "Gitalk1.1.4" —> https://github.com/gitalk/gitalk. Also, doesn't really look like Disqus to me.

Yeah, it uses Github issues: https://github.com/bmabsout/blog-comments/issues/5

How can we make this happen with ipfs itself? :)

CRDTs! https://ipfs.io/blog/30-js-ipfs-crdts.md