Forget weapons and armour. Using any kind of equipment during a duel simply isn't classy enough. Either you go into battle wearing nothing at all or you're a disgrace to Yharnam.
No but seriously though: naked battles between players in Souls games is definitely a Thing, and I'm happy to report that players such as Kite Nordenskiold continue to keep the tradition alive. I'm particularly fascinated by how one even communicates that they're going to lay down their weapons and clothes for a good ol' fashioned fist fight -- but Kite pulls it off, and the results are hilarious. Fast-forward to 2:45 if you simply want to watch the gentleman's duel.
Unfortunately actually killing someone without a weapon is incredibly difficult -- so eventually, one of the combatants felt the only way to end the battle is via suicide. Regardless, it was an admirable effort which must be commended.
Those of you interested in pursuing noble duels such as these might want to start by testing the waters first. Do your opponents return gestures? Do they immediately launch into attacks? If not, try to slowly introduce the idea to them by being friendly, saying hi, bowing, and then taking your clothes off. Maybe it will work. Or maybe you'll just make it easier for your enemy to kill you. Turns out honour is kind of risky!
Bonus: a clip by Steven Ihde that shows why real gentlemen shouldn't gloat after a win either:
P.S. Yes, ladies can be gentlemen too. It's about the spirit of the thing, you see.