Cap'n Kobold
Hero
Generally the quarterstaff is held along the last quarter-ish of its length (although this is possibly not anything to do with the name.) Its not good as a military weapon, but has great advantages against civilian swordsmen.I'm a good longswordsman (I mean the historical longsword, not the D&D one) *at all*, but my first impression when I saw that one handed wielding was "a longswordsman would *murderise* this guy". Granting advantage in certain tremendously unbalanced matchup could make sense.
I think a quarterstaf should be lighter than that 8 pound monstrosity incidentally. I agree that the one hand use is odd.
Incidentally, it's now believed that quarterstaves were used in the middle age not in the eastern style (holding it with both hand 2 feet appart in the middle) but rather like a greatsword (one hand near one tip, one hand about 1/4 of the way up). It essentially made the quarterstaff like a very long and very fast wooden sword. They did some tests with it and they found that a man armed like this could keep at bay two swordsmen, thus the defensive reputation of the weapon. What we see in movies is inspired by the "bo" wielding from the east and that can be an effecive style. But it's not how it was done in Europe... and I think that that style is just as cool if not cooler![]()
And no, it can't be wielded effectively one-handed. I don't care what Gandalf was doing with it.

I'd just view anyone using the "D&D quarterstaff" in one hand as using a jo, or other short staff rather than an actual quarterstaff.
A historical longsword pretty much straddles the line between bastard sword and two-handed sword. Its pretty much exclusively used two-handed (There are specific maneuvers such as the spear-like stab shown in the video, or striking with the pommel or guard that can be executed by one hand but actually fighting with the sword requires both hands.) Bastard swords, arming swords and such are what D&D longswords are, and can be used one-handed or two-handed.But a dnd greatsword can't be used one-handed (at least not by the rules) so wouldn't that make it more like the claymore? I thought the former dnd bastard sword was more like the historical longsword. The 5e longsword almost seems right with it's versatile property, except that nearly everyone uses it one-handed in practice.