People should learn from their example.

I'm not sure if it's that they have no PR experience in the company, or just don't consider StackExchange/HN/Reddit to be worthy of a serious effort.

IMO, this is the kind of thing founders should handle personally once it happens. Maybe guided by a PR person or an investor, but a founder giving an adequate response gets graded on a curve, and is thus a lot more effective than a completely polished PR/marketing person.