Maybe it depends on the topic a blog is about or something else but I have a small blog about photography ( https://50mmf2.com ) and I've had only one slightly negative comment.

My blog isn't getting much traffic or many comments though. I would imagine that as something gets more popular it attracts more negative attention. That being said, the more popular niche photography blogs ( mainly about film photography ) have largely positive comments as well.

Promoting just an email will yield a much lower communication rate. Which might be OK in some cases but it's also nice to receive comments. As long as they are not terrible...