... if you're posting it on Instagram, probably. If you're posting publicly WITH corporate blessing, definitely.
If you're not some publicity seeking narcissist who's just doing their job and is not actively filming your bowel movements, no.

I've got no problem with anyone who doesn't wear the hat or jacket; I've flown with more than a couple of new FOs who don't even have a uniform yet. I never said anything to them, but they were always quick to explain why they weren't in proper uniform ... I imagine it's because they've already had a few pilots comment on their lack of uniform.
But when one is posting stuff publicly as a United pilot with corporate approval, that's subject to a different level of scrutiny. If you're going to post stuff where every single person sees it, you need to follow ALL of the rules.
Remember when the female scab who wrote a book or two and had a website posted some pictures she took from the flight deck? She got fired. She appealed and never got her job back. Don't post stuff for the public to see if anyone is going to interpret it as a violation of the rules.

I know I do stupid things from time to time, but I don't have any active social media accounts because I don't want an additional level of scrutiny that would highlight my mistakes.
Hold yourself out to the public and you are going to have a lot of eyeballs looking at you. Some of those eyeballs are going to be critical.
Sure it's petty, but I'm not a fan of this type of publicity for the profession. I know I sound like a jerk, but in my opinion, his narcissistic behavior, as posted on the instagram links posted here, degrades the profession. (I don't actively seek to view his posts).
I'll leave you with this short thought - WWSD (what would Sully do). IMO, that's the standard all Professional pilots should strive for.