Not "random people online", but I've got a few friends I think of as "terrifyingly smart", and one of their common characteristics is how they've all, in areas of expertise I've been investigating/researching/working in for weeks or months and which they have barely a passing interest in, quite obviously thought about a problem I'm describing and thought through a bunch of the obvious options, categorised them, and made conclusions about which avenues are workable and which should be discarded, and come up with either a workable solution or options I'd not even considered yet - all just in the course of a conversation over coffee...

(Somewhat frighteningly, two of those people are doing that at Facebook right now...)