Well, I guess buying at high prices and selling at low prices is common to traders. Although disadvantageous, it requires quick action to sell. You should be aware of such a thing if you do not want to lose a lot of money.
Why would people buy high and sell low? That would make you lose money and likely all of your money will be gone in minutes.
Not even sure why people want to go for this topic, I don't think it is good advise nor good strategy.
If you bothered to read the original post its not his advice, its a statement of fact that most noob traders do this. OP's advice is to put orders ahead of time to avoid emotions taking over.