If it has been thoroughly tested and it is and has been consistently profitable and they have the discipline to follow it, then there is no chance that they will "wipe" their accounts.
Given that so few "traders" have plans to begin with, and given how many fewer have plans that are thoroughly tested (something more than buy if it looks like it's going to go up), the above may seem incomprehensible to someone who has not gone through this process. But it's how one makes a living at this trading his own money (if he's trading OPM, he can come up with just about anything that sounds good, whether it actually works or not).
Even a system based on indicators can work if the above criteria are met. A system based on planetary alignment can work. But, getting back to the subject of the thread, the lag inherent in indicators must be accounted for through extensive testing. One may believe that indicators forecast or predict or whatever, but unless that belief is supported by more than anecdotal data, the system will eventually fail.