Pastebin - Still an early version as I haven't made much auto-comments, but it does the job. Yeah, I don't mean to replace you work, made some improvements to make it more usable to me and thought about sharing the changes. Also, I learned how local storage works in extensions because of you... :-)

Spotted a bug: In-line editing a greeted comment saves the greeting within the comment. I won't fix this...

Attempted to fix a bug where "Welcome to SITENAME!" was inserted twice, doesn't reoccur...

Fixed a bug where you were unable to click the option bullet or edit the entry after import/export.

Fixed a bug with incorrectly loading the visibility of descriptions. Works 100% now... :-)

This is how I do this now. Not going to implement this myself because I dislike an extra click...

Implementation thoughts: See my answer for a local storage based extension. Use a new syntax (eg. ##) that when read is stored as a comment with description "header", then when reading such comment you could embed all subsequent non-header comments and easily have expandable groups.