RAW and RAI:
Players are not intended to use such skills against one another. It can be done when you need to make the paladin look the other way, or demand order, but it should mainly be done within the fiction not within the die rolls.
From a playing perspective:
We usually roleplayed it out with a bit of meta versus meta when someone has the bright idea to use social skills on a sheet and the d20 versus an actual player. We knew what the rolls meant and would often break the 4th wall in those cases just to reinforce that using skills in that manner was "frowned upon"
Eventually the joke got old and people stopped trying to roll social skills against one another unless it was entirely in jest.
Overall, the players settled into classes and stats that they could actually roleplay out (which means I never play High CHA characters normally), leading to much more interesting situations of how would a low INT or WIS person interact in a high stress situation.
For Diplomacy: Check: You can change the initial attitudes of nonplayer characters with a successful check.
For Bluff: Check: Bluff is an opposed skill check against your opponent's Sense Motive skill. If you use Bluff to fool someone, with a successful check you convince your opponent that what you are saying is true. Bluff checks are modified depending upon the believability of the lie. The following modifiers are applied to the roll of the creature attempting to tell the lie. Note that some lies are so improbable that it is impossible to convince anyone that they are true (subject to GM discretion).
Circumstances Bluff Modifier
-The target wants to believe you +5
-The lie is believable +0
-The lie is unlikely –5
-The lie is far-fetched –10
-The lie is impossible –20
-The target is drunk or impaired +5
-You possess convincing proof up to +10
Try Again: If you fail to deceive someone, further attempts to deceive them are at a –10 penalty and may be impossible (GM discretion).
Check: You can use Intimidate to force an opponent to act friendly toward you for 1d6 × 10 minutes with a successful check. The DC of this check is equal to 10 + the target's Hit Dice + the target's Wisdom modifier. If successful, the target gives you the information you desire, takes actions that do not endanger it, or otherwise offers limited assistance. After the Intimidate expires, the target treats you as unfriendly and may report you to local authorities. If you fail this check by 5 or more, the target attempts to deceive you or otherwise hinder your activities.
While possible to use Bluff and Intimidate against another player, Bluff clearly gives an advantage within party members (You know the rogue is a liar so why wouldnt you be at least doubtful) and Intimidate assumes you arent already friendly (most party members are already friendly with each other) would by rules allow them to pursue contacting the authorities afterwards, and even then only would otherwise offers limited assistance further curtailing how useful it would be against party members.