I've noticed myself doing this in a number of situations ever since and I suspect many of you have as well.
It's the downside to living a web-enabled social life and I do wonder how the experience eventually affects everything we do if, after a while, no one sounds truly authentic, but rather like a self-conscious public version of authentic.
Particularly because so many people don't do self-conscious very well. At least not yet. All too often there's some cringe-inducing verbiage signaling the speaker wants to remind us that they're a truly deep thinker. The underwhelmed endorsement of something the endorser suspects they should be heartily endorsing. Or the blatant attempt at currying favor with someone whom the supplicant thinks will make them seem hipper or at the very least smarter.
And these are people, not brands.
What do brands get to sound like, especially because they do need to be eternally self-conscious?
For many brands, spontaneity is not an issue. They are in more or less perma-response mode, answering questions/dealing with problem from their audience and providing a "helpful" response. We have zero expectation of spontaneity or authenticity from brands online, though there are admittedly times when we'd like to see someone do a Steven Slater and tell a difficult customer where to go.
But since that's not happening, all we're left with is the nearly identical voice of brands all trying to be cheerful and helpful and likable leavened by the occasional rogue CEO (think Gary Vaynerchuk or Mark Cuban) who've made themselves the brand.
I'd argue that's still a big improvement: I'll take the uniformly perky voice brands adopt online today over the deafening silence of the last hundred years.
As for people... it may all go back to the "village" theory, which basically says that for thousands of years we all lived in little villages where everyone knew everyone else's business 24/7/365 and that it was only the brief period following the Industrial Revolution where that rhythm got disrupted and that our current American lives, filled with anonymity and reinvention are not that healthy and actually somewhat deviant.
And so it may just take us some time before we get used to living in "village" mode again and not caring that everyone is going to know what we're up to before we regain our ability to live unselfconsciously, albeit publicly.