This is a very narrow view of mentorship. Mentorship is incredibly selfish: often the person doing the mentoring gets more out of the conversation than the mentee...case in point. Here, the author was challenged on basic ideas that led him to think more broadly about what he assumed was obvious. This could and often does lead to more creative thinking and applications in his company. As long as he doesn't do this all the time, I think it's silly to assume that a CEO should spend 24/7 working on a company. In fact, it's degenerative, unhealthy, and produces poor results for companies (as many studies show).

Personally, I think there should be more focus on when he did it rather than the fact he did it. If he was at the office doing this, then I'd agree with you. If the workday was done, then I can see an hour of his personal time being fine.

You don't practice what you preach, dude. How is this helping you make payroll?

Do you also object to parents reading Hacker News? What about doctors or nurses?