The only reference I could find by @ChipMixer is stating chipmixer.io is not their main domain. But there is nothing stating that the .io version does not belong to them, so I am assuming that ChipMixer.io is, in fact, owned and controlled by @ChipMixer
We were under DDoS attack. Tor service was not affected.
They probably do own chipmixer.io but, if they do, it's probably just to stop anyone from doing a phishinng attempt with the domain name.
I think .IO needs less information than .COM does when it's registered.
This being said, I wouldn't advise using anything other than the official chipmixer.com and the official .onion domain names as using anything else would just be foolish. They may have the .io name in case they need to move from .com if they get DDoS attacks on the main site.
(chipmixer.net and chipmixer.org appear to be owned but parked also - not sure who owns those).
Questions as serious as domain names should not be left to speculations. It should be so factual and direct for people to know for the sake of posterity. If what is happening is exactly what @darkstar_ is calling an attention to, then this is the time to either debunk or confirm it. If any one fall victim of it, then the blame would to chipmixer as to why they didn't come out with a statement which would suggest some level of connivance which would be more difficult to control then and reputation in this crypto world is a fragile thing that can be lost so easily. #my opinion.