Oh yes, very good strategy for a startup fighting against another startup. I'm sure a letter written by a lawyer will be effective at least in draining Cushion's bank account. Unfortunately in cases like these Cushion doesn't have legally much to go on because it's not super unique design. Only reasonable course of action is to raise awareness and he chose to do that. He also chose to do that without naming the competitor which is of course very classy and smart from Cushion's point of view but does very little for Cushion as a whole. This is a great opportunity to play the competitor out of the market by turning their lust for shortcuts against themselves. Proper way to "return the favor" to the competitor is to get other people telling others about it.