Ask HN: What are the signs that someone is intelligent?

Came across this thread in Reddit, alas, most of the answers were really disappointing: instead of signs of being intelligent, the answers were "good qualities dumb people can very well have, but especially nice if displayed by someone intelligent" (Examples: "Not condescending", "Make YOU feel intelligent", "Dare to say I don't know", etc.).

Wondering if I could learn from better quality answers here in HN.