Ah yes, you are correct - I had forgotten the "put".  Thanks for that.

Now I have a follow-up question.  I have been able to add a new post to the topic, but the post always is authored by the person that created the session.  I would like to have that comment authored by someone else.  I have tried the following:

        RAMTopic topic = (RAMTopic)asset.getForums()[0].getTopics()[0];
        RAMPost post = topic.createPost("title", "description");
        RAMUser user = session.getUser("username@company.com");
        System.out.println("Comment author is " + user.getName());
        post.setSubmitter(user);

I have also tried extracting the posts array from the topic, adding my new post and then setting the new post array with
     topic.setPosts(newPostsArray);
but get an error "Method is not executable by the client".

I think

RAMUser user = session.getUser("username@company.com");
System.out.println("Comment author is " + user.getName());
post.setSubmitter(user);