That "editor" link disappears when you start typing so you need to click that "editor" link on the top right corner of the the text box before you start writing your post.
If you don't do that first, you have to use Markdown to style your post.
If you forget to go to editor before writing your post, you can copy your entire post into clipboard with your mouse, hit delete, click that "editor" link and then paste the text back from clipboard. Then you can use "editor" and "RAWHTML".
Thanks