While I executed my QED here deliberately, I've left more than a few duplicate comments on laggy connections and/or bogged-down browser sessions.

Other elements of HN's design and workflow make detecting this difficult. Rather than returning the user to the comment they'd just posted, or its parent, you're returned to the discussion root.

Catching typos, incorrect tags (I keep having to remember that _this_ doesn't emphasise content), etc., would be far easier if the renderd comment was presented.

Solving this as a browser / HTML built-in would be most ideal.

HTML though isn't stateful. By design.