According to this, "Bitcoin Segwit2x does not have any built-in replay protection, but Coinbase has implemented our own replay protection system. You can safely send any BTC or B2X from Coinbase without worrying about replays on the other chain."
But will they have any replay protection for receives, as well as sends? I don't imagine they can do anything to prevent a transaction sent to them from being replayed on both chains, but at least they could detect the replay, and credit both currencies to your account.
I'll probably try to avoid this, but just wondering if I have some backup protection if I make a mistake.