This is a bit strange: in my answer here, the MathJax has incorrect vertical alignment:
But when I go to the edit page to try to fix it, the preview shows the correct formatting, different to what is shown in the post:
But it's (of course) the same MathJax code, so this means either the MathJax renderer is wrong in the post or it is wrong in the preview. (I think it is wrong in the post.) In case it matters, I'm using Google Chrome.