Not sure how many characters per post you get, so since this is big I risked to err on the side of caution. Condense these two posts if they are back-to-back and need to be/can be.
Armor Class (AC) measures how hard it is for your enemies to land a significant blow on you with a weapon or a magical effect that works like a weapon.
Do people in your games worry about significant blows with a weapon being landed on the players?
Yes. Either form the DM or other players when they become annoying or disruptive.
You can see a gnoll archer crouching behind a rock wall, but the wall makes him more difficult to hit, because the wall gives him cover.
Can players in your games see a gnoll archer?
Harbinger or Underdark? One of those DDM sets if not the Chainmail or Pewter/lead/Raladium variants are clearly visible yes.
Close attacks include two basic categories of powers: weapon attacks that damage multiple enemies with one swing, and powers created from energy that flows directly from your body or an object you carry.
Have you seen players creating powers from energy that flows directly from their bodies?
Ever pissed a female gamer off? You don't have to see the energy to know and feel the heat and burning aimed in your direction.
If you are trying to move across an unstable surface that isn’t narrow, you instead fall prone in the square you started in.
People fall prone a lot at your table?
We love slap-schtick!
Whenever you use Insight, you’re making a best guess as to what you think a motive or attitude is or how truthful a target is being.
Why is there a skill for that, then? Players can guess whatever they like, without rolling a die!
I feel the same way. There are plenty of useless component in the game that are not needed other than that provided you have a decent DM and players.
You can use such a skill to remember a useful bit of information in its field of knowledge or to recognize a clue related to it.
How can the player remember something, unless the DM's already told him once before?
I would figure he went to school and had parents. Maybe read a book?
When you ride a creature, you gain access to any special mount abilities it confers to its rider.
My living room's too small for that sort of carry-on.
Don't have pets or kids, eh?
The result of your saving throw determines how close you are to death.
That's ominous!
In this day and age it is even all the more true than ever.
Wouldn't all of these make more sense if, sometimes, the word 'you' in the PHB referred to the character instead of the player?
-Hyp.
Wouldn't they have made sense if the context of my previous posts were read rather than twisted?
Even better would have been to use proper grammar in the books so as not to confuse the reader [player] with the character?
The result of your saving throw determines how close you are to death.
Do the characters roll dice? Do the characters throw something when they are about to die? The players of some games may throw a fit, but the character does what?
I would suggest to proper word the phrase instead for the reader as per technical writing guidelines suggest.
The result of your saving throw determines how close your character is to death.
This properly addresses the reader with the proper context. It does not use the word "you" or instances of its other forms in different ways in the same sentence. When you make a substitution of another word, you should maintain the same substitution through your sentence rather than changing the words meaning midway through it.
"Your" indicates something belonging to the player now in both instances in the sentence, while before the variations of "you" was referring back and forth between the player and the character.
After all of this are you still really trying to dispute that you need only roll the proper skill checks to pass a skill challenge?