Takes some extra work
Every time you reply to any message, you have an option to sellect if you want your username replaced with a number.
If you start a thread with a number, you should be careful to sellect the same option when posting subsequent replies.
That means, you should reply by clicking on the blue "reply" button, and not use the "Post reply" form available directly below every message. That simple form does not allow for special options.
If you discover you posted a reply with a wrong username, use the edit button to edit your message.
Edit message function is available only in the single message view.
You access single message view by clicking on the link above the message.
Yes, keeping your identity hidden takes some extra concentration.
One way to avoid the problem, is to have 2 different usernames.
One username to use when you want to stay more anonymous, the other username when you want people to recognize you.
Webmaster