Umm, dude, you need to get your facts straight.
REAL authentic swords WERE light. Historical examples of swords from museums and historical manuals are proof of how light swords were back when people actually used them to fight. The majority of "replica" Swords (and cheaply made ones at that) are usually heavy, because to many people heavy = better and they think it means more quality. The process of making a sword back in the middle ages vs today is VASTLY different and no one knows exactly how it was done, the closest anyone got was the late Paul Champagne who sadly passed away just a short time ago.
Your "carbon folded" katana would probably break if you actually used it on anything in real life.
fyi, dont just google it or wiki it (based on your post, you didn't even do that) the carbon folded katana is one of the most powerful blades there is (factoring how it keeps its edge for thousands of years and the dual structure of the blade makes the edge rigid and razor shape while the back side is soft and supports the endurance of the blade.)
if what you mean by "fact" is actually opinion go a head. I have seen and held an hand forged blade, its heavier than die cast.
besides, you mean to say that swords in museums are examples of how they are "actually light" then you need to explain to me how some one goes about getting museum curators crack open highly prized and protected artifacts to be held by any common person who walks in. btw, what do you mean no one knows how it was done, my granpa and my step dad make knives and swords by hand. just because you don't know of any blacksmiths doesn't mean that the art is dead.
not really intending to troll, but that post was so full of it there was little I could do to stop my self.