You get penalized points but cant readily tell unless you pay attention. For instance, I was leatherworker and equipped a hat that was favored for classes besides mine. The hats stats were 16 defense and when I equipped it I only got about 12 from it, and I was higher than the optimal rank for the hat (optimal rank only affects stats if you're lower than that rank).
So I only got 12 instead of the full 16 (which I couldn't tell I was being penalized on the armor but had to add it up myself when I equipped the hat).
Edited, Sep 27th 2010 9:11pm by PinkMermaid
PS3 - Lil_Mermaid_Girl