Change Request informationChange Suggestion System, if not then have a look at this document.
NOTE: Change suggestions, have also previously referred to as 'Tickets' so you might still find this term around the site.
The photo-owner and moderator see the full conversation,
any other registered user will just see the initial suggestion (not the follow up comments), and its current status, but will not see the status of actual changes while the suggestion is pending (as they could have been applied).
However the suggester will see any follow up comments if the photo-owner or a moderator choose to 'copy in' the suggester (I think this now defaults to on), but will always see the closing comment.
A pending suggestion can only be commented on by the photo-owner or a moderator, and only a moderator can apply suggestions from the change suggestion and/or close it, (but the photo-owner can apply the changes separately anyway).
Photo-owner is notified of the suggestion (but can opt out), but receives any moderator comment (no opt out). As mentioned suggester will receive a copy if photo-owner or moderator choose (no opt out), similarly for photo-owner comments (which the assigned moderator always receives).
On suggestion closure photo-owner receives a notification (no opt out), with a list of changes applied and the closing moderator comment attached. Suggester will also always receive a copy, thanking them.
(if a moderator makes a change and applies it in one step, then photo-owner is sent a notification with the comment -(with same opt out))