Seriously, you need video? Not a wonder they do it
If we are going to follow ISF rules, it wouldn't take much evidence, but either a video, yes, or several screenshots. How else are we to do this? Take someone's word against another player? We can't do that, but this level of evidence is only one reason why I said earlier that the MT doesn't currently rule on this issue. Without double chasing being blocked by the programming there are hard problems with enforcement. First of all, we will have to define the offense and define the punishment that works for our site. Do we block after the same amount of moves as the ISF? Do we allow more of an offense? Perhaps we allow it for ten minutes to match it to our draw refusal rules? No matter what qualifies as a violation, since double chasing is not blocked automatically no one will understand when they get punished for something the site allows.
Then the next question is what happens to the person doing the double chasing? Does he get a warning at all? Or does he merely lose the game? Or something else? There are questions.