From my understanding, it is trivial to create an arbitrary number of Mercury servers, any of which could be acting evil.
If that's the case, then I have misunderstood their operating model. I was under the impression that everyone would be using the same centralized server being operated and maintained by the Mercury team themselves, just as you do when you use a centralized exchange or a mixer. Therefore if there was a provable scam accusation against them, then the entire project would be moot, and it is relatively easy for them to build up a good reputation over time.
If, as you say, anyone can host one or more servers and act as a statechain entity, then I agree, the security model is poor at best. With no way of punishing someone other than reporting that server to be a scam, at which time the user in question can just spin up a new server, then I would not be depositing any coins to this wallet.
dkbit - do you know the answer to this?