there's no reason that a) needs to happen in a public
    comment and b) that you cannot provide an email for
    people to reach you at

I blog a decent amount, and I don't like getting emails about my posts. I'd much rather have the discussion publicly. When we talk in the open other people can contribute to and learn from the discussion. Putting lots of effort in a careful back and forth conversation with a reader is much less worth it if it's a private 1:1.

(If I wanted to talk about things where people couldn't be honest in public it would be different)