Real money (person buying the mogstation item) is being traded for something in the game (in-game currency or items), so yes, that's RMT.

If someone actually sends a gift without getting any compensation, that's okay, but as soon as they pay out real money and get compensation in another form (in-game currency or items) then it's no longer a gift and that is essentially a trade and RMT.

Does SE care though? Probably... as mentioned above they weren't at all happy about wedding bands being sold in game so I don't know what they may/may not do, but I would personally just play it safe and not get involved at all. But that's me