"If people already know something, there's no point in posting it." I think you expect something else from HN or this discussion than I do. I think it can be h

"If people already know something, there's no point in posting it." I think you expect something else from HN or this discussion than I do. I think it can be helpful to remind other people of facts in a discussion, lest they get carried away. Not every human exchange has to consist of novelties. If I do maths, I might remind myself that 2+2=4. I have known it before, but chose to recall that knowledge at opportune moments. In discussions, other people can help with the recalling, it does not imply that the other parties were ignorant before. It is just about adding another perspective. "I have nothing to go on, other than what you write" In such situation I tend to resort to common sense. Does it seem plausible ("have merit") what the other person is saying? If yes, I might remember it as an interesting thought (not as established fact), or if it seems useful if true, might take further steps (Google) to verify it. It's not that hard, and you don't have to insult the discussion partner. Here is another idea: "That sounds interesting, do you by chance remember the source for that?" See the difference? But hey, it is the internet, there is no human on the other end.