When you try to edit a Ticket, besides the description textbox and options, the reply box is still there. That reply box should disappear, like comments do.
The reply box is there so that you can edit a ticket and change the ticket status in a single operation. For example I am now closing this ticket and changing its status to 'wont-fix' through the edit form :D.
Ok, in that case yes. But still: if you are editing a comment, you shouldn't see 2 textboxs in the screen. Try to edit this, and see what happens.
There is no way for you to distinguish between the two cases:
There is no way for the page to guess that you want to edit the ticket but you don't want to post a reply. And since you cannot separate the action of editing the ticket status and editing the ticket description, this really a wont-fix.
Ok, it seems I misunderstood before, you want the Comment text box at the bottom of the page to disappear, when you are editing another comment.