@Urouge:
Ok, I feel like it's time to revisit my understanding of this topic. We all know the basics behind mantra (CoO) and armor haki (CoA), so there isn't a whole ton of debate to be had about them. Kingbition (my own word for CoC) though, is still a little more up for interpretation.
The question that always pops up regarding kingbition is "ok, it knocks out fodder, so what?" So, there must be more to it. At first glance, Rayleigh's comments about how the most powerful people in the world tend to have the ability make it out to be more of a badge/medal than a useful ability. So the shock of people who've seen him use it can be chalked up to "this kid has the potential to be top tier? Yikes." At least, that's the safe answer.
But the question that always comes next is "so what about its potential in combat against people who are too strong to be knocked out by it?" Anyone without that level of strength wasn't really a threat anyway, so it's reasonable to assume there's more to it.
The first thing that has to be looked at is the way Rayleigh describes kingbition/CoC in chapter 597 as "the ability to intimidate your opponent." Logically, we can assume that the ability attempts to terrify people to the point that they pass out. This would mean that those who don't pass out are not immune, as they still feel like they're in the midst of a terrifying presence. Being scared means not being able to fight at full potential, so already we begin to see some benefits to the ability even against strong opponents. Even still, pretty dull.
Having followed the train of logic to this point, though, the true power of the ability begins to manifest itself in regards to the other two colors of haki. One major theme of Skypeia was figuring out how to defeat someone using mantra. Ultimately, what it comes down to is the mantra user's "focus" and making him lose it. Once a user gets scared or distracted they lose their focus and thus lose their grasp on mantra until they regain their composure. Put simply, being scared fucks with a person's ability to use mantra. While armor haki doesn't have the same heavy development that mantra has, Rayleigh connected it to "spirit" which is likely to work in a similar fashion.
In conclusion, I believe that kingbition (CoC, whatever you want to call it) is indeed a terrifying ability among haki users as it affects the strength of the other two colors of an opponent. Perhaps an edge in intimidation alone may seem only mildly useful, but when that edge also provides an edge in mantra and armor haki, it could potentially mean a world of difference in what would be an otherwise even fight.
I like the way you put this. I've seen the idea before and I think it makes a lot of sense, not least because I'd personally like it if things around Haki don't end up branching out too much as I've also seen people speculating about but are kept to a few rather basic concepts. There's some translation that puts it like "overpower the opponent's will/spirit" and that seems to fit pretty well in with it affecting the Haki strength of the opponent.
On CoC damaging Whitebeard's ship… Rayleigh did say that it is "the user's spirit manifested" or some such, didn't he? It's like a crushing pressure on the opponent's own spirit (which will cause them to faint if they're too weak-willed, or as Jozu said, aren't prepared for it). Maybe a truly top-class Sovereign Haki (and we have good reason to think that Shanks possesses one such) can even lightly extend to objects in the vicinity, manifesting the spirit so strongly.
Oh, and I'm in agreement that CoA was used to remove Caimie's collar. I guess I could see it being CoC somehow as well, since Ray looks rather intent, but as Urouge put it that's delving into "anything goes since we don't know" territory and I'm usually hesitant to go there. Though I suppose one could make the argument that Shanks on the Moby Dick is a clue to CoC being able to do something like that.