Some things I've noticed over the years:
- Maturity makes a hell of a lot of difference in how someone RPs.
- Empathy makes a HUGE difference between someone who can only "roleplay" as themselves or actually portraying a character that is different from themselves to the point that they can play multiple characters and you wouldn't realize it's the same player behind the screen (this is what I always strive for).
- Skill at storytelling and writing can make a huge difference too.
- How you talk in ooc chat can clue people in to who you are irl faster than anything and will affect how they respond to your character. (I tested this myself by hiding the fact that I was the same person behind two different characters for a while in my old FC.)
- My FC back on Atomos was about 1/3 female players (fewer server wide); Balmung seems to be about 1/2.