Comment editing feature for Paid and Permanent users. A few details: "Only the comment poster can edit a comment."; "A comment cannot be edited if it has been replied to or frozen."; "When a comment is edited, a small note is put at the bottom of the comment text with a timestamp of when it was last edited."; "Anyone who would normally receive a comment notification when a new comment is posted to a thread will [automatically] receive a notification when a comment has been edited."