Thanks for the responses. In reality it was a hypothetical question to see what others thought.

I had forgotten that everyone will most likely have fiddled with a strategy before setting it live. Even though this is exactly what I would do!

If brokers have the means to spike to stoploss levels then that could kill any strategy dead once larger positionsizes are being used and it is worth brokers doing. Makes it feel like a rigged game if that actually happens. I guess we have to hope that with hundreds of thousands of people placing positions that the brokers book would be so varied that they would win as much as they would lose so wouldn’t bother.

So the question really should be that if you coded the holy grail strategy would you happily share it with the world?