So you actually discriminate against the more skilled player?

Interesting. I think there's definitely a cultural shift going on. I'm reminded a little bit of
this story.
Couple of observations:
1) D&D is not chess. For many people the goal is not to "win" as such but to engage in the setting to the greatest possible degree - I think both Umbran and Pemerton touched on this effectively.
2) Is the player really more skilled? If the player's charisma on the character sheet is 8 but he's playing it like 18 - he's not playing skillfully, he's not playing the character he made. Wouldn't the skilled player be able to suppress his natural charisma, or at the least play it down to the level the character is supposed to be?
I tend to filter the player's comments and actions through the stats and rolls of the character when deciding the situation (to account for the very real phenomenon of 2 people - saying exactly the same thing in exactly the same situation, where one is taken as witty and brilliant and the other taken as a crass buffoon). An exaggerated example:
Suave the Bard (Cha 20, Diplomacy +15):
Player (addressing countess Famina and rolling a 30 on diplomacy): Hey there.
DM as countess Famina: My goodness, you’re such a cad! You must come to my next ball where I can introduce you to my marriageable daughter.
Krug the Barbarian (Cha 8, Diplomacy -1):
Player (addressing the countess Famina and rolling 14 on diplomacy): Hey there.
DM as countess Famina: Away from me you unwashed ruffian. One more word and I shall call the guard!