Good remark. The most obvious place for me was the help web page. But searching in that place for "reply" at that page did not bring me further. I have used Google to find the answer.

I would like to reply to a message, but there is no reply button.

I have read the reason is I just got an account here and that I first have to post to the newbie section. However, there is nothing for me to contribute to the newbie section. Therefore, I think this newbie rule is ridiculous.
Sorry for bothering you with my message.