They can solve complex open-ended tasks, and formulate long term plans that take into account information from multiple sources.
I understand that this is not a very high bar to set in comparison to other working professionals, but nearly everyone in the tech industry, and most other people who have a desk in a company's head office, are working at a level above the average person. Many of the posters on HN are biased by their personal and professional contacts and have an incorrect impression of what an IQ of 100 looks like, or how smart the average person is.
Going back to what I said originally, being smart is not the same as being infallible. Smart people can get themselves into all sorts of trouble that everyone else would have the humility and common sense to avoid.