In the MathJax editor, when ENTER is pressed (e.g., after typing an equation), then the editor closes and the cursor is moved to the start of the text box. I would expect, instead, that the cursor would be placed immediately after the equation that was just edited.
[Edit: This issue is also reported here.]
On a related note, when ESC while the MathJax editor is open, it should close the MathJax editor but instead it opens a prompt to close the Add/Edit window.