RT Privileges

To all,

I have a privileges question. I have been working with the 

understanding that “ModifyTicket” would allow a user to modify any part
of a ticket, including status and changing Queues, but not adding
Comments or modifying Custom Fields. Those last two privileges seem to
be reserved for other rights, “CommentOnTicket” & Group right
"ModifyCustomField" respectively. If I give a user or group the
"ModifyTicket" privilege in a Queue, they CANNOT modify a ticket custom
field (in that Queue) unless that custom field has been applied to that
Queue AND they are in a group that has the “ModifyCustomField” privilege
for that custom field. They CANNOT add a comment to a ticket unless they
have that right as well. Am I correct in all of these assumptions? Thanks.