As far as I know, you can only edit your original post within 24 hours of it first being posted. So if a solution arrives three days later, you can no longer edit the original post. The link for “edit” doesn’t even display. You can go down from “options” to “edit” when just looking at the discussion under “your discussions” but that leads to a page that says “Hey, you don’t have the permission to do that”.
It sure would be nice if you created the thread, to still have access to edit the original post later than 24 hours so you can mark it Solved.
As for the permissions problem, all I could do was yell “sudo” at my monitor unsuccessfully.