[vova_hn2]

Ask you IRL friends or colleagues from your job "hey, do you happen to have an HN account?"

If the discussion is related to a public project, like in the examples in this comment: https://news.ycombinator.com/item?id=47303604

...you can use existing communication channels (website, readme on github) to ask people for an invite to participate in it.

[throwaway2037]

I am pretty sure that none of my friends nor co-workers read HN. Whenever I have shared stuff, none of them have heard of HN.