I have just returned home after a two week vacation to the US. While staying at Lake Placid (NY), I trained with the local CH guys and they were fantastic. Not only did they allow me to train with them but they went out of their way to show me a variety of their techniques. We can all learn from other styles and it is amazing to see how many similarities there are within the various disciplines. I will incorporate the new techniques I learned into my teaching. Most MA schools welcome visitors and are very happy to allow them to train while on vacation. Take every opportunity to broaden your knowledge.
I agree, absolutely—we can and should learn from what each other are doing; that's how progress is made, no matter what the area of activity is.
But in a sense, it's not that surprising that there are many parallels across different MAs. The task is the same, really—defend yourself from attack—and there are, as many people have observed (Bruce Lee most famously, but I doubt he was the first), only so many ways for an object structured like a human body to inflict damage on another such object, using the limbs as the weapon. At the level of basic tactics, all MAs run into the same limits: how joints move, how many ways you can attack if you're using certain parts of your body to defend, etc.
Where the styles really differ, I think, is in strategy. My sense of Combat Hapkido is that it definitely belongs to a family of arts where the primary weapons are forcing movements against joints with limited freedom of movement. The striking arts—Karate, TKD/TSD and a few others—may use tactics that employ such movements, but the payoff, the
punch line (so to speak, lol), is a finishing traumatic strike that either damages a limb sufficiently to incapacitate an attacker or, more seriously, interrupts some vital activity—breathing (knifehand attack to the throat), vision (claw strike to the eyes, with
sincerity) or consciousness (punch or hammerfist to the temple). It's in the area of strategy, I think, that whatever stylistic differences between MAs exist that are really worth talking about are to be found...