For one thing JP thread is much more organized, they post the threads in appropriate forum section is one thing NA we got threads doing this as well but most are posted in the General Discussion area.
Example: 2355 threads in General Discussion on JP side compared to 11039 threads in GD on NA side.
They try to name the title of the threads so you can tell what the thread is talking about instead of "HELLO", "I HAVE AN IDEA", "DISAPPOINTED" where you gotta click and read to find out what the thread is about. Those will definitely not help getting rep posting replies on it imo.
People try to stick to that one thread instead of making multiple threads.
Not all but people do try more to search for certain thread topic and post within the same thread to keep it clean. Only time they separate a thread is if they get into a debate and think that should be discussed in another thread then they will go ahead and do that.