the reason they see you is that while tanks that require staying still to turn invisible do go completely invisible tanks that are always invisible actually aren't invisible just transparent you can easily see that if you see a rogue tank in arms race mode I guess some people have better eyesight
Hey, if you are an operator you can press `c to be or not to be shown on the leaderboard. I do not know whether that cancels out incognito, but it may work.