I believe that might seem like the reasonable behavior for most forums. I use my forum, though, as a Q&A site for my college students studying mathematics, statistics, and data science. Learning Markdown and LaTeX is part of the point.
I have no doubt that many of them want to use the rich editor. They really need to use the Markdown editor, though. So, I’m glad I can enforce this by setting the Markdown editor as the default and hiding the toggle switch with CSS.