I think the personality section of a CS is quite important... as a guideline of sorts. I usually think of maybe 1 or 2 strong personality traits I would like my character to have and build with that. If I write a character who is of a 'nice' personality type however, I'm not bound by that - a nice person still does shitty things - just the same as a shitty person probably does nice things. If I see someone in a roleplay acting really really far out of what they wrote in a CS I might bring that up, same as if I see them being completely one note I might try and push them to explore.