This just seem impossible to exact decide ...
For one, humans have average IQ 90-110, yet sometimes there are person who have abowe 140 ... how can you decide when is your character just gifted genius, and when you simply put all your points to good stat not care at all about making sence? :-/
Also ... i dont like that stat being called Intelligence to be honest, it seem like everyone i know expect characters with lower intelligence to be at least demented or something. -_-
Yet intelligence is much more than ability to make whole, complement senteces ... its about your character memory (therefore remembering more spells for a day), abylity to learn new things, abylity to understand so far unknown things, or solve problems, etc. :-/
Not every barbarian who have intelligence 8 have to be Neanderthal telling just "me smash, me eat". :-/
Im sorry, its certainly interesting topic to talk about, but it seem to me impossible, and kinda childish to try determine exact spot where role play ends, and power play starts.
Honestly i would rather play with someone who can provide me interesting character, good storyreacting and fun, even if his character is strictly set for maximal effectivity ... than someone who will spend an hour every level he gain to determine wich spell, or wich stat he should take, to not look too power-playerish. :-/
