I've never understood the appeal of guestbooks and commenting on Wordpress. Static HTML is a wonderful medium for getting your message out, do we need the validation of visitors commenting?
Emailing comments is possible even with a comment system, assuming the site owner discloses it. But it is invisible to others, as most blogs are not going to curate emails into a "Letter to the Editor" section of the website.
Substack is an email newsletter platform and even that has a comment system.