in my opinion, most all highly intelligent individuals - especially those in the public eye - must have one
I think I understand this. I used to run a small but active online community. So not fame at all, not even "guy in a tiny band that has 15 people show up for their shows" famous. Less than that even. But sometimes I'd go to parties and people would know who I was and I didn't know them. That kind of thing.And I did start to develop a hint of a persona. Like you say it was kind of a must. Having strangers that know who you are coming up and talking to you is definitely flattering and also definitely a bit intimidating so you quickly develop a... a mode you go into or something.
Not a calculated Raoul Duke thing at all. In my case it was more like the different "personas" any person has - the personality you wear at work vs. the one you wear around your parents vs. the one you wear around your significant others. I was always being myself, but you definitely calibrate yourself a little differently for different groups.