Could be fixed already since I'm using 6.2 still.
Could someone try this on newer versions to see if it applies:
Edit a user, choose to "Grant Mod Rights". Do not actually assign them to any forums.
Now grant them admin rights.
Now revoke admin rights.
Does the user show up in a group search for "Moderators" still but has been changed to U_Status of a "User"?
In 6.2 the dorevokeadmin script checks to see if the user is a moderator by checking entries in the w3t_Moderators table. Moderators with no entries in this table are turned into a U_Status of "User" instead of a "Moderator" and the U_Group value of -2- is not removed. The user then still has moderator group -2- access but is a U_Status "User".