Mathjax bug?

The following inline math is written as ‘A=a, b=B’: \(A = a, b=B\)
But the CHTML renderer working in Microsoft Edge or Internet Explorer on Win 10 rendered as “A=A, b=b”. The SVG renderer works fine. Which is this a bug of Mathjax or Microsoft?

(The default renderer in this page is SVG. The renderer can be selected by right click on the math expression.)