I don't agree with the person you're replying to; it's unfair to permanently ban people from competitive play for online cheating they did when they were younger (although not that much younger in this case).

however, without overly expensive and invasive methods of detection, plus unpleasant rule changes, what you describe isn't feasible. there are too many ways to cheat, and people who are already smart enough to play at a grandmaster level are not only going to find these ways, but excel in them.

I don't have any evidence to back this up, but I would be extremely willing to believe that plenty of high-level OTB cheating has gone on over the years, especially with money on the line