If we're discussing moans specifically, I'd have to say that most JAV actresses I've come across don't. They kind of whimper and cry as far as I can tell. I'm not talking about BDSM either. I've seen "normal" porn starring Elly Akira, and she whimpers for no apparent reason. This makes her (and others) very difficult to watch for me. Although Yumi Kazama doesn't whimper, she doesn't moan either. There is something I like about Ryoko Murakami, but I can't really call it a moan. Ai Mizushima (my avatar) tends to use a whine which I guess could be considered a moan in some circles... But which is my favourite? I was going to say Ryoko Murakami, but as I type this I might just say Maki Tomoda.