"Peeker's Advantage" is a reality of online gaming. Because of network latency (ping), the player swinging a corner sends their position to the server before the server can update the player holding the angle.
How to Abuse It: If you know an enemy is holding a corner, do not slowly walk out. Use the A or D keys to aggressively swing wide. Because of Peeker's Advantage, you will actually see the stationary enemy on your screen a few milliseconds before you appear on theirs. Combine a fast, wide swing with a perfect counter-strafe, and the enemy holding the angle has no mathematical chance to react.