What's noisy is the information you get rapidly, not necessarily the outcomes. If you (stupidly, of course) buy and short-sell the same amount of some asset, your outcome is noiseless but the information you get from watching what actually happens to the asset is still noisy.
What's noisy is the information you get rapidly
Doesn't that entirely depend on what kind of information you are interested in?
Another month, another rationality quotes thread. The rules are: