Oh lord, another person grousing about the supposedly-OTT thinblade. In truth, it follows a standard convention for an exotic weapon: take a martial or simple weapon and upgrade it by one step at the cost of a feat. In this case, the thinblade can either be seen as a rapier with its damage die increased by one die-type (which is the difference between a battleaxe and a waraxe), or as a longsword with its threat range increased by one number (same as the difference between a dagger and a kukri).
Now, granted, this ill-conceived racial Weapon Familiarity nonsense takes a sledgehammer to the whole concept behind exotic weapons by giving superior weapons away for bupkus, but that's not a problem specifically with the thinblade. The same is true of the waraxe.