Thats for the Screenshots - Ive taken a look at the whole action set in your account and I can see whats going wrong here.
Firstly - Your Character Function for the Users.EmailSignature action is contained After the Send Email action - It will need to be before the send email to make sure the merge takes place. For Reference, the 'Send Email' action is action sequence 46 in your account.
Second, the Character function itself. You'll need to be using the Action Result that you are using for the Email Body to replace merge fields (ie. what is in