So, one of the How To videos mentions that you should never blow your nose in public in Japan. I think it also mentioned not talking on your phone whilst on the train and not dressing like you're about to go for a mountain hike.

Anyway, I'm wondering if there are any more of these sorts of things. In particular I was wondering about knuckle-cracking. I'm a habitual knuckle-cracker (I enjoy both the winces it induces in everyone within earshot and, believe it or not, it actually feels quite good), and I recently cracked my knuckles in front of a couple of Japanese friends and I think I saw them exchange a look, so now I'm worried.

If anyone could clear this up, I'd be very grateful!

Tom