The quote links back to an old thread with more discussion on the subject, but basically this has been a "word of mouth" rule for a long time. I have no idea why it's never been stated explicitly in the rules, but it basically boils down to scam-prevention. I'm not trying to say you have any intention of scamming anyone, Kylan, just that such is the mindset behind the decision.
Pretty sure it's written in the rules somewhere. I'll locate it. EDIT: I found where it used to be written on the Residence flags page, but forgot we recently redid that page. I have added it to the Official Rules under General Other Rules.
