Hello

1. A non registered user create a new thread.
2. A mod edit this posting. --> "edited by mod" is shown
3. A mod changed the category --> "edited by non registered user" is shown

Until here I can confirm your observation. I create a thread as an unregistered user in one browser and alter the content of the entry as the admin in another browser. After this first edit the username of my admin-account is shown, if it's not disabled to show the admins name. After changing the category as the administrator in a second attempt, the name of the (unregistered) thread opener is shown in the entry-is-edited-message.

4. A mod changed the category AND edit the posting --> "edited by non registered user" is shown

After changing the content of the entry and altering the category again, the entry-is-edited-message says, that it was done by the admin, not by the thread opener.

Tschö, Auge