Smurfing as a form of rating manipulation is not allowed, but if you are paired against an opponent much lower rated, then you just play your best and still win if able to. Titled players win against much lower rated players all the time (especially when they are streaming and playing viewers). I wouldn't call this "smurfing" though. I would just call this playing against someone much lower rated and yeah that happens sometimes, but sometimes you'll also be paired with much higher rated players, so it balances out.
Smurfing?


Its actually high risk / low reward for you, and low risk / high reward for them --
If you win --> you win very little // if they win --> they win a lot,
if you lose --> you lose a lot // if they lose --> they lose very little.
It keeps the ratings from getting slogged down. Everyone make mistakes and blunders, especially when moving fast, and you never know if that 300 player is just a prodigy that is at the beginning of their climb to the top. Always play to win.
I'm only 1000 rated on Blitz, but I'm wondering whether I am allowed to beat 300's in rapid. It feels wrong? Does anyone have any advice please?