I do not work for Coinbase and do not in any way speak for or represent them. This post was hastily written and is probably full of typos!
This is my attempt to clarify the possibilities that might be going on, based on various Coinbase employee statements.
First, I should highlight that there has been a good amount of confusion created by the replay attacks going on between the "two" Ethereum chains. So much so that it seems to have confused just about everyone, including me, as to the details of what's going on with Coinbase's ETH/ETC (and other ETH/ETC).
I put "two" in quotes because at the moment it's more like there are "1.25 Ethereum chains" because of the replay attacks, which are causing almost every transaction to get mirrored on the other chain. Replay attacks are possible because Ethereum's hard fork did not take steps to make Ethereum transactions invalid on the original chain. Instead, all transactions are valid on both chains unless specia