Is the bannig system harsh?
One strike you're out. First time is the last time. So long as you play safe you shouldn't get banned. I've played with the mod off and on since the game launched and the mod was created and only one of my accounts got banned. The reason for that was because I used the features in the mod for the Jubilee events they have. Tips: Don't use any of the attack or defense multipliers because that will raise your overall EP and in the rankings if you have a higher EP than the huge whales, then you'll get flagged and banned.
Like I said before, don't use any of the features for the Jubilee events because that's considered PVP and they can detect fraudulant activity.
Realistically, only use the God Mode and Instant Win features. They're more than enough for all the content in the game. The Wither Enemies feature is pretty pointless since you have the God Mode and Instant Win features.
I know that was a lot but if you follow my instructions you shouldn't get banned at all.