Yes. You can keep one for yourself and one to whomever you want.
* Don't send your private key to someone you don't trust.
P.S. Main point in ChipMixer's post in Reddit is timelock [1] transaction, not multisig.
[1]
https://en.bitcoin.it/wiki/TimelockGreat explanation.
Basically, the proof section of the Chipmixer site is its main provably fair mechanism, since it publishes private keys every single day to prove that bets aren't rigged. What you can do is create a multisig wallet with one of your own private keys and the other as Chipmixer's private key, and voila, your coins aren't technically yours anymore.
I have a question - if your coins are in multisig at the time of a hard fork, what will happen to your funds? Is there any way that Chipmixer can offer this service trustlessly as well, for example with nlocktime?