The Japanese players on FFXI (on Caitsith, at least) keep very much to themselves. They rarely use says or shouts, and it's difficult to get them to party with NA players in Qufim and beyond (lv 20+). The ones I have partied with, however, are much better players than most NA players I've partied with randomly--friends not included. Also, 90% of the time Jp players will just use the autotranslate instead of actually typing kanji or kana, which is really what you're supposed to do.
Oh, and while NA copies will display Japanese text, it only allows input of English text, so you'll have to use romaji to type back in Japanese.