The Duct Tape mod causes the subject's sent messages to be unreadable. For 10 minutes, the player's messages is replaced by sequences consisting of m's and f's. The player would also be unable to edit Signs and Doors, Broadcast, private message, and write on Bulletin Boards, Mailboxes, Donation Boxes and similar items.
Only the 
Duct Tape grants the Duct Tape mod.