Why is backtesting foolish? As long as you haven't used the data you're using to backtest in any way, it seems like a reasonable way to test your strategy.
Your point is perfectly valid and is a useful addition to my prior post.
Otherwise, they could be an indication of future performance.
Just being visible in the OB will cause other people to act differently from if you weren't. This of course has a profound effect on strategies relying on passive orders.