I've met a few extremists on TSR. Have you? Watch
No, personality isn't what others entirely perceive it to be.
Personality is like a set of characteristics, each with a certain meaning (which has a general consensus upon / sentiment behind it, anyway) , so you can attribute it to them, with some accuracy.)
Nothing is permanent, everything is impermanent. Your personality isn't fixed, it isn't anything. It's just a collection of behaviours, or traits, instigated by chemical responses in your brain. It isn't consistent and if it isn't consistent, is isn't, strictly speaking, anything.
I can be certain about (a few things about) some personalities right now, in present, and can make predictions I am confident in about certain aspects anyway in the future if I see little reason as to why it might change.