The principle
Reflect their behaviour back at people and they are forced to see themselves. Mirroring teaches lessons no lecture can — and infuriates opponents who recognise the move only in retrospect.
The application
Copy a competitor's tactic with a small twist, and you neutralise their advantage while making them feel imitated. Used carefully, this is judo. Used carelessly, it is mockery.
The defensive tell, how to spot it being run on you
When a rival starts producing work, language, or moves that feel uncannily like yours, do not assume coincidence. The mirroring is sometimes flattery and sometimes intelligence-gathering with attribution. Move your work somewhere they cannot see the draft.