And that nails the best reason why it is a Good Thing to be able to tie a user to a post.
Your help is likely to be more effective if people are able to ask you questions about it, and if you are able to easily notice that someone posted a request for clarification. Therefore posting anonymously limits your ability to provide assistance to others.
Furthermore if you aquire a reputation for good posts, people will go through your historical posts and run across posts that they would not otherwise have read. Which again improves your effectiveness.
But that said, PM experience and Perl experience are rather unrelated. For instance I have more XP than chip, TheDamian, gbarr, Dominus or merlyn. But I do not consider myself more knowledgable about Perl or more experienced in programming than any of them...