Quote Originally Posted by tuggyne View Post
Examples: the older, larger, and more powerful a red dragon becomes, the harder it is to realize you should use cold damage on it.
Perhaps this is a sort of penumbra effect of Frightful Presence - the dragon radiates so much ancient and awful power that your brain starts shutting down slightly just for being near it, and seemingly obvious facts like "use an ice spell dumbass" simply don't emerge from the chaos of your thoughts the way they should. Even if you're immune to fear, perhaps that only arrests the macroscopic effects, and you still have certain subconscious reactions to how horrifying and dangerous the thing you're intentionally moving closer to actually is. (Also this check only applies if you've never fought a red dragon before, or if you're somehow having trouble recognizing that this is the same species as the dragon that you did fight before.)

which is in turn more bewildering than a black bear, purely by virtue of being more dangerous.
Precisely. Dangerous = bewildering. Most people are not coldly efficient and logical in the face of deadly peril; even professional soldiers who have been in and out of the war zone a hundred times still have some degree of difficulty coping with the stress every single time they again face the prospect of being blown to bits with a mortar shell.

A draft horse is harder to understand than a pixie
Okay, that one I'll give you is utterly wrong. Perhaps there should be an adjustment of -2 for animals and vermin and +2 for extraplanar creatures, or just something to do with the general commonality in an area.

Worst of all, by strict RAW, you could argue that a Human Fighter 20 is almost impossible to identify as human by anyone under level 10 or so.
It'd be fairly obvious to rule that class levels don't stack with race levels for purpose of this identification - it'd be one check to identify him as human, which would ignore all his HD since there are no human Racial HD, and another check to identify him as a Fighter based on the trappings of his trade; that might be the difficult one, but class-based checks might well be easier rather than harder at higher levels. (I'm not sure whether class identification checks actually exist in RAW but it'd make some sense to houserule them in, perhaps a Knowledge: Combat skill is defined as allowing you to guess what fighter bonus feats a character seems to be properly equipped for or to take the corresponding stance when a fight begins.)

are you really going to elaborate on all the possible ways of finding out about a creature as being circumstance bonuses?
Yes. If the GM is going to try to tell me I can't recognize a dwarf, I'm damn well going to fight for every inch of ground as best I can manage at the time (how hard I can rack my brain will depend on how much of a piece of Swiss cheese my brain happens to be that day).

If so, that says the rule (which is designed to measure your knowledge already) has failed. You're left with "does he have a reasonable way to have found out about this in backstory/roleplaying? if yes, auto-success; if no, auto-failure".
The rule does an imperfect job of what it's meant to accomplish; big surprise. It doesn't mean it has no applicability. The calculation isn't binary all the time; in some cases the range between know/dunno is so narrow as to be practically nonexistent, but in other cases there are a lot of uncertain factors, which is when the dice come into play. If the rules were complicated enough to serve as a perfect model, we'd never find the time to read them, nor remember everything we read. (Though it would be helpful to define a set of rules in such detail if you were programming a computer game that could automate them.)