When using the Vim editor, I cannot switch back to normal mode from insert mode.
Since releasing support for Vim and Emacs modes in the writeLaTeX editor, a potential issue has come to light with users who have the Chrome extension "Vimium" installed.
If you're using this extension, you may find that after inserting text you're be unable to revert to normal mode -- the standard commands ESC or CTRL-[ may not work.
We have found that after disabling this extension, the writeLaTeX Vim editor works as expected.
For more details on the Vim and Emacs editors, see this blog post.