Many manga series on mangafox have got such a thread. As the name implies you can post your thoughts on and questions regarding the latest uploaded chapters here. Questions and thoughts regarding older chapters should be fine, too. Even a little bit spamming/offtopic (jokes, private matters and happenings,...) should be okay, if it somehow connects to something ontopic in the thread. Just don't overdo it.
And try to add somewhere in your post or in the title, to which chapter you're referring to, if others haven't done it already and it's obvious.