Delete a comment.

Authorship, not permission tier, is the gate: you may delete your own comment, and holders of issues:close may moderate anyone’s — someone has to be able to remove a departed colleague’s. A bare API-key call carries no human identity and so cannot prove authorship; it needs issues:close.

The delete is soft. The comment stays in the thread as a tombstone with body: null rather than vanishing. Returns 204 with no body.