Nothing is preventing you from creating a chatroom by yourself and posting a link to it inviting the involved parties into the chat room.
(limitations regarding chat privileges are of course enforced - there are discussions about that as well...)
With regard to guidelines on "noisy" comments - it all depends on the context. Comments should only exist to aid in the understanding of the main post. Any comment that goes off onto another topic could be considered noisy. I remember reading a post (or a comment ;) that said something to the effect of -
A comment should always be posted as the last comment on that thread. It should not be a question provoking more discussion (unless of course it is directly related to the understanding of the post).
Trying not to get carried away with my explanation but essentially the existence of a comment might suggest that the post itself does not fully encompass the subject at hand. If more explanations are needed perhaps an edit is due for the main post to make things clearer. I'm not saying that comments are not necessary - quite the contrary - It's really helpful for all parties involved to be able to have a place for quick, short interactions in order to clarify things. Arguments do not clarify anything...
Another (slightly over generalized) example of what could be considered a long and "noisy" comment thread occurs when dealing with users who have little experience with the platforms/technologies that they are working with. An answer to a user fitting that description might need further instructions on how to implement the solution that was given, however the implementation of a solution might warrant an additional question. One could even call this a chameleon question.
Comments should only exist when further explanation is needed about a post. As soon as a comment veers off the explanation of the solution, it is noise and even one noisy comment is "too many comments".