Own ask.com how can I contact someone or message someone on here?
You can't you can comment this isn't a social site
Next time you see someone's question or answer & you want to leave a message for them, go to their Profile & Follow them. Then you can see their questions or answers & leave a message that way.
Sonshine is right, following them is a great way to keep up with someone. Also, the best way to have a conversation with someone is in the comments section.
It's not like FB. Just keep a "lookout" for that persons response or question and then you can respond.