Bai,
Some users found it confusing to be asked to reply and then find out they had to login/register. We are working on a more subtle way to point this out. Like show the buttons differently. It will evolve as we go. The idea is to show users the functionality is there for registered users without confusing people.
Another thing I am not too pleased with is that the "login/register" screen has "register" before login, so if I use tab-space-tab-space it tries to register me as a new user.