This is actually a great idea. It prevents the earning of merit to display a signature being a "one time thing" - you can't just make one good post and then go back to shitposting for months on end. It forces users to consistently strive to make better posts to continue to be allowed to display their signature. It would vastly cut down on people buying merit as it no longer becomes profitable to continue to buy more every 2 weeks. It means the users levelling up all their alt accounts will rapidly run out of merit to send.

As bitart mentions, probably one a month rather than one every two weeks would be more appropriate. And it would need to come with an increase in merit sources, particularly in some of the local boards which get far less than their fair share of merit. But yeah, I like this idea a lot.