There's no trust required since you would be able to detect this because the coordinator would have to block all other inputs from joining. We already discussed this, remember?
I remember, Kruw. I remember very well. Do you?
It obviously can't. If your coins are refused, you have no idea if it is due to Sybil attack or if Coinfirm has simply decided your coins are naughty and are not allowed to be coinjoined.
Let's just leave that as is. I really don't want to turn this into another Wasabi thread. You couldn't provide sufficient responses back then, I predict that you can neither do now.
Let's say the coordinator selects both C and D, (both owned by Alice) for the same coinjoin round. How should she respond?
That's fine, I guess. There would be a problem if all premixed coins entered the same coinjoin. But, even if it is problematic, Alice can simply refuse to sign the transaction.