Like others have said on the thread, it’s best to confirm if it is a dust attack before sending the coins back to the sender address. Quick question - are there wallets that really have “remark space” for users to leave notes? I haven’t noticed this feature before, maybe it’s because it’s not something that would interest me.
If it's dust, it won't be worth to spend back to the sender.
Dust attack, the coin sent to the address is usually worth very little, very small that sending it back will cost closely the same amount of Bitcoin, Imagine refunding less than $0.7... worth of Bitcoin back, if not that transaction fee is now very cheap.