...The higher the profile and the closer the capo gets to the fret, the sharper it will be. Ideally, you need to get the capo parallel to the fret and only as close to the fret as needed to prevent sting buzz. This lessens the effect of the strings being pulled sharply over the fret and therefore reduces the sharpening effect. Placing the capo right behind the fret will eventually weaken the strings at that point. ...

Sorry Peter, but that is just plain bollocks.

Ideally, the capo should be placed as near to the fret as possible, almost on top in fact. The critical thing is to have the capo adjusted so that only enough pressure is exerted to seat the string firmly on the fret, it does not have to be depressed all the way to the fretboard. The further from the fret the capo is placed, the greater the mechanical advantage and the greater the likelihood of the string going out of tune.

As far as your observations about weakening the string is concerned, words fail me ...

Any serious guitarist will have changed the strings long before any hypothetical "weakening" could possibly take effect.