It has a thread here:
https://bitcointalk.org/index.php?topic=877.4140Local boards are added as and when needed when there's demand for them. A lot of reports have been coming in about nonsense posts and bot spam in the local Japanese thread and it would probably be exploited by sig spammers and farmers just like the Chinese section is. Sadly, a lot of local boards are ripe for abuse due to only having one mod or none at all in some cases so I'm often against them unless there is huge demand for them, which is hard to gauge as people often have ulterior motives for them to be created.