Player Vitalik wasn't banned. "ЧМЧ" simply means that he can't participate in tournaments, if I'm not mistaken.
P.S. The case with Andrey is telling. In general, it's not the player who should prove their honesty; that would be self-demeaning. Instead, they should be presented with evidence of their dishonest play.
It seems like common sense, something even a seven-year-old would understand.
So, there are idiots everywhere - don't make this an exclusive trait of Heroes of Might and Magic.