%% Most likely the trader; unless it follows/profits trends or counter trends + gets in a sideways slop chop trend[aka barbed wire range].
Here is a thought: Most high flying systems on C2 start to lose around age 5-6 months. And some of them lose really big, and almost no system wins after that point really big. So if you start to reverse these type of systems at around that age, there should be a positive expectancy for the outcome... The reason I advocate more systems because there will always be 1-2 going against the rule...
Lost money is forever lost, and have to be accounted for and then more in your winners, which is unnerving for long-term holdings as they're not yet cashed in! Where the money went? To the sharks of course!
Consider a system that makes one trade and it''s a loser that buys at 80 and sells at 30. Reversing this system would boost your account. The problem is that most systems win certain trades and don't make money on certain trades. They are not regular and you don't grasp if they will make money on a certain trade. If you need to test this yourself, use a system that makes long trades. If this system buys at 30 and sells at 80 you won't hAve to worry about comission. Go with a 250 period hull moving average. Buy on the open of the bar after price closes above the average. Sell the reverse. Watch what happens. You will either have a profitable or unprofitable strategy. Change the open/close rules and determine if it makes a difference. I have never Ever Seen a profitable system. Fellows always blame it on the trader, tho. Such nonsense.
What do you consider to be "opposite" system? Go long vs short and vice versa? The trade is not only long or short, but there are other parameters i.e. SL and TP. In other words changing long to short is not "opposite" system.
An opposite system for me might be modelling out a different prob distribution of a stock to fit an options position.... so I might be looking for a quiet setup to put on an at-the money fly that pays me well if XYZ settles around the same price 2 weeks from now. so I would be backtesting a filter x>y and keep getting mediocre results, I would reverse it x<y which changes win % from 48-55% which in options is more than enough to trade off of. In above example it is just a time stop. ie 2 week hold.so punisher,et al --it is not neccesarily reversing buy into sells. just finding peaks and valleys in the distro of the stock by reversing filters.
Each trade consists of many parameters, so flipping one of them is not really a "reverse" strategy. That's why most say that reverse to losing strategy is also likely to fail. Now, one could wonder if flipping ALL trade parameters would be truly reverse strategy, but I'm not so sure it is. My basic intuition say it's a "different strategy", not really "reverse".