I have tried changing the security level, so that the From: is filled in automagically, but it just does the same. I have also tried emailing directly to the address where messages are supposed to go, and From: comes through just fine, so I assume it is something in the code here on LJ.
Is there anyway to have that fixed? Or, if nothing else, have the link in the User Info say something like "Send {user} a text message on his/her cellphone/pager. (Please include your name in the body of the message)"?