The comment feature is very useful to request clarifications on questions and answers with the goal of improving the quality and value of the commented question or answer. It's less useful for discussions that drift away from the actual question or answer - that's what the site's chat room is for.
Few new users realize how awesome the chat is; it has many neat features you're not used to from other chat systems you grew up with! You can even chat with people who are not even online, so you don't have to be in the room yourself for very long. They'll be notified the next time they visit any page in the Stack Exchange network.
If you need help with the chat system, you can simply post a question in the chat room.