If you have the ability to sense another human's emotions you can often tell when someone is being authentic or not. Set and setting are also important. Authenticity is closer to honesty about yourself rather than some kind of self-expression. I am still authentic if I don't mention my hobby of collecting records while I am at the gym. I am not authentic if I start making up whatever will impress you.
> But we dislike influencers and the like because while they are (often obviously) inauthentic, they try to hide that fact under a facade trying to make it seem like it's their "real expression".
IMO, most people dislike influencers because they fall into the category of people who are outwardly pathetic. In any sort of human interaction desperation is seen as unattractive and wrong. Influencers are desperation boiled down into the highest concentration. They are fake, inauthentic, not because they aren't who they are but they try so hard to dial up everything about them to it's maximum.
> Doing a paid sponsor bit is ipso facto inauthentic
If I am doing a paid sponsorship for beard care equipment I am authentic. This generalization doesn't fit.
> I'm sure the Ryan in front of the camera is different than the Ryan I'd meet at the bar: more polished, calculated in choice of words, presenting self in the best light, because that's what we all do in the limelight.
Someone who takes the time to create an entire blog dedicated to a topic will likely be 90% similar to what you're reading. Of course there is nuance in human interaction but someone that dedicated to a particular craft will most likely obsess over it even in person.
I understand your post is some sort of philosophical discussion on authenticity. Maybe in some textbook sense you are right. However, I have had more authentic interactions with people than inauthentic interactions. If you're close with anyone at all in your life you have also experienced that. The systemization of everything (through what you call "radical self-expression") is creating a bunch of pseudo-intellectual naval gazing on what is fundamentally a simple topic. Authentic people are honest people. You can often tell right away who is lying and who is not. The computer in your head has hundreds of thousands of years of evolution to help you with that.