Toribash
good

only clan management+ should be able to change your clan's tag/name
seems like a bug

op is in a different clan, think it overrides the permission

made the post yours, try now
Sometimes this happens to me when I am logged in then go to the clan thread and it doesn't show the edit, so I go to forums and it shows me as logged out, so potentially the forums logged you out because you're logging in elsewhere perhaps?