Uh no, actually for him to NOT write what he did would make him a dick. So what he wrote is really the only thing he could have said without coming across and conceited and arrogant.
You registered an account to make this statement? Writing "I'm one of Stripe's cofounders", as he does in his profile, would not "make him a dick" but it is interesting that he didn't do so here.
Honestly, I just don't really like the self-aggrandizing ring of "I'm CEO and cofounder". And I don't think it's particularly relevant most of the time. Yes, I'm a cofounder, but the important part is that I work at Stripe—alongside many others.
#humility
I would have gone for something like 'sup bitches this is Patrick Collison'. Perhaps thats why I'm not the CEO of Stripe.