@Riger
> There are several swords meant for armor. They're usually large and have blunted edges, though. Like the estoc, for example
What your friend probably meant is going through ring mail.
> Just dent it hard enough that the armor harms the chewy center for you
I doubt the point of a sword and the weight behind a thrust would be enough to dent plate armor. You're supposed to thrust into the joints and gaps in the armor. Plate armor doesn't actually cover 100% of the front of the body.
If you're suggesting to thrust at a certain point over and over again, well, that's not actually feasible in combat. You're asking to get wrestled to the ground and have a rondel dagger driven into your armpit or through your eye socket.
> Heavy blunt arms like maces and morningstars were insanely heavy.
Unless you're talking about two-handed bludgeons, they aren't. They just have more weight concentrated on the head but overall, are only about as heavy as any other sword, including the katana. It's just that swords have their weight more evenly distributed.
> I've even seen a few huge swords in museums that had no edge at all, but did have two much smaller spikes sticking out of the sides to pierce when swung. Like a lower case letter T. I've seen a few crucifix shaped swords meant for smashing and piercing armor, as well.
Maybe ceremonial, decorative, or executioner swords? Only way to know if a particular shape of a weapon was used in battle at all is if you could see one of them has visible signs of use. I've seen unspectacular halberds that look like they have been whetted hundreds of times, all hung up on at a little corner of a museum.