I don't know what forum software you used, but on xenoforo, when a new messages are posted on the thread, you'll get a button at the bottom (with text like 'new

I don't know what forum software you used, but on xenoforo, when a new messages are posted on the thread, you'll get a button at the bottom (with text like 'new messages have been posted since you loaded the page, click _here_ to see them'), loading the new messages without having to reload the page. Though I feel forums are more geared around asynchronous conversation anyway.