One point to bring up that may be missed here,

WHY would an officer use a sword during the gunpowder era? (specifically an infantry officer with a line unit, NOT a cavalry officer)

The answer to that question speaks directly to the likelihood of ever seeing sword vs sword combat.

And the answer is: Self Defense.

An officer's sword in that era served the same conceptual role as a pistol in the era after it.

An extremely close range, personal defense sidearm.

See, an officer wouldn't carry a rifle in those days. Rifles were for the infantrymen on the line to shoot at the enemy.

Its NOT the officer's job to shoot at the enemy.

Its the officer's job to stand back, supervise, direct, coordinate.

To draw an analogy, you can't be conducting the orchestra is you're too busy trying to play one of the violins.

An officer trying to stand on the line and pick off the enemy probably isn't properly doing his job of directing his men.

So officers don't need rifles.

BUT... what happens when the battle goes really badly, and now the enemy is overrunning your position?

Now that officer needs something to defend themself with.

A rifle... maybe not the best option. Not the ideal weapon for close quarters melee distance, and too big and cumbersome to carry around all the time in case anyways.

Nope, but if the enemy breaks through and gets into arms reach, every man clawing and stabbing at each other distance... pistols and swords become VERY useful.

And THAT is why swords and pistols became associated with officers/leadership positions.

In the modern firearms era, we DO see officers start to carry traditional firearms, but even then, we still get hints of the "not a line troop" nature of those weapons. Example, WWI it might common to see leaders carrying pistols more so than rifles. By WWII you might certainly see officers carrying rifles, since they were less cumbersome than they used to be, but even then, by T/O you would typically see officers with something more like an M1 Carbine or Thompson Sub. Smaller, lighter, easier to carry, shorter effective range, but higher rate of fire. You're not picking off enemy soldiers at a distance, but if the bad guys overrun your lines and start storming the HQ tent, you have enough close up firepower to kill everyone coming through the door, and/or maybe blast your way out of there.

Interesting tidbit that I can't speak to as confirmed fact, but I have heard referenced by a lot of the old Vietnam era vets; shotguns. So, even in the Vietnam era, some officers carried pistols, some M16s, but then shotguns got popular. With the whole "personal defense weapon" idea in mind, the saying/logic was "LT, if some sh** ever goes bad enough that YOU have to reach for your pistol, you're gonna wish you had a shotgun."

Except...

>And THAT is why swords and pistols became associated with officers/leadership positions.

Of course, a lot of other officers decided they DID want to just carry an M16 like everyone else, because in a Vietnam style of war snipers were a constant fear, and you didn't want to wear/carry anything that made you look like "someone special" from a distance.

TL;DR:

Sword on sword combat in the rifle/musket era seems like it would be a reasonably uncommon battlefield occurrence.

Foot officers really only carried swords as personal defense weapons. It wasn't their job to directly engage the enemy troops.

Thus, if an officer was in the thick of it, hacking away at the enemy, he was likely either

A. Leading his men on a charge through the enemy lines

B. (most likely) desperately trying to fend off the enemy that was overrunning his own position.

In either case, A or B, said officer was probably fighting some untold number of riflemen, NOT seeking out his equal opposite across the field for a gentlemen's sword duel. (which still isn't to say that officers didn't learn and train single sword combat, just saying it wouldn't be all that battlefield relevant)

Hmm... In a nice little "Hollywood got that right" moment - IIRC in the 1989 Civil War move "Glory" Matthew Broderick plays a Union officer, and there was a scene of him practicing with his sword. They did NOT show him practice man to man fencing against some fencing dummy. Instead they showed him on horseback, chopping the melons off the tops of a line of fenceposts at a gallop, as if riding through a crowd of enemy, taking out men on the ground. Nice job, director guy

One more note:

>And THAT is why swords became associated with officers/leadership positions.

That is why it was a big deal in the U.S. Marine Corps, for them to issue the "NCO Saber". The very existence and issuance of a sword for non-commissioned officers, i.e., Corporals and Sergeants, was an acknowledgement that the Marine Corps saw NCOs as unit leaders, with leadership duties and authorities. NCOs could be "in charge" of people and missions. This is a concept that wasn't common in a lot of services, and still isn't fully accepted in some militaries today. Which is to say, almost all militaries have ranks equivalent to Cpls and Sgts, but NOT all militaries have a culture of entrusting Cpls and Sgts with true managerial authorities and responsibilities)