I don’t think it will be enough. I’m always amazed by how easily people forget such information. Users are often impatient and skip the intro, and even when they don’t they forget much of it after 10 minutes.
This seems easily fixable: a change of the title to “latest topics” would help imho. “New topic” is imho clear enough, but how about, for example, “New conversation”?
Agree. Here’s my small contribution:
The messages icon can change the color and shape depending on unread messages: (I guess it could be a grey
comments-o icon for no unread messages and a blue
comments icon when there are)