Hnews has already gotten into how this isn't really a jamstack issue, just an issue with a 100% static site.
While the piece is kind of flawed, it made me realize that the people arguing "well at that point why not just use a CMS" miss what I like about my site. I use Horst Gutmann's webmentiond, which I run myself. It's webmentions so not exactly comments, but everything about comments applies. I could have all the static content in an S3 bucket; I don't, because for right now it's just as easy to serve out myself. However, the static site with a comment system tacked on is nice because there is perfect separation of concerns: webmentiond manages and stores the data for those comments, and on my site I only have to futz around with the display of that data. This is something that for everything I hated about disqus comments, they got right: you just plugged them in.
I wonder what else that comes packaged Out Of The Box with Wordpress could be nice as its own little module for a static site.
Comment with a webmention, or with commentpara.de