I'm not sure what's going on with them. Their figure eight north-south night pattern should make CHOK next to impossible here in the Chicago area. As a practical matter IME,they're nowhere near as strong as they were when they were running day pattern at night (which I'm pretty comfortable in saying probably happened on multiple occasions since 1995). But they still turn up here from time to time. My guess is that CHOK is not running day pattern at night, but instead, the night pattern isn't as tight as it's supposed to be.
There used to be another AM station in Sarnia that was accused of cheating. CKT Y on 1110. I don't know if they were guilty or not, but IIRC, we used to have an engineer on this board from WTAM in Cleveland (1100) who claimed they were running higher than authorized power and trashing the WTAM signal. I have no idea if that was true or not, but CKTY was a relatively easy catch for me. It's all a moot point now, since CKTY has moved to FM. "Back in the day", CKTY was country, CHOK eas oldies
(For those unfamiliar with the location of Sarnia, it's at the southern tip of Lake Huron, across the Saint Claire River from Port Huron, Michigan. I've crossed the border there on multiple occasions, via the Bluewater bridge, but never stopped.)