I dunno, I see several posts a week on HN where I think "I bet your cofounder/colleague/boss/investor will know this is you if they read it" questions every week, many of which are far more contentious in subject matter, so this kind of questionable judgement isn't that unusual. The stupider point is that he was seriously considering turning down an apparently better environment and $15k more because Uber gets more mainstream press attention and has a more inflated valuation. But we were all naive about the world of work once...

As a CEO I'd want candidates getting a second opinion privately so they were reassured when they decided to accept my offer, and the only reason I'd see "not ruling out much worse offer from other company" as a major black mark is if being savvy in commercial decisions was an important aspect of the role.

A savvier candidate would probably be trying the "That's great, but I also have an outstanding offer in a similar total comp range from Uber. At this stage I think I'd fit much better into your team, but if you could move a little on the financial side of your offer I'd be much more inclined to confirm without waiting have that followup conversation with the Uber hiring manager" approach anyway. And quite possibly succeeding...