MathJax has started centering displayed equations. For example
the display equation is centered. Previously they were aligned left.
Looking at the generated the code we see
<div class="MathJax_Display" role="textbox" aria-readonly="true" style="text-align: center;">
<span class="MathJax" id="MathJax-Element-2-Frame" style=""> ... </span>
the centering is in the code rather than in a style sheet.
Aligning equations to the left is the desirable format.