How to have separate private comments for nodes apart from the general comments? I have a specific requirement.
Apart from the general comments which everyone can view or post for my custom node I also require private comments thread which will be shared only by the node created user and selected few.
Using the same comments form will not work as it will be viewed by all.
Any inputs on achieving this?

Thanks.
For Drupal 7 see the Reply module. It lets you create your own set of "comments" attached to any Entities you want.

With some custom code you could limit the field to a specific user role or set of users. Be sure to read the README in the module.