Misaligns \begin{split} inside \begin{align}

Created by: andersk

Real LaTeX alows a split environment inside an align environment to share the same alignment points, but MathJax 2.1 doesn’t. Compare the renderings of

\begin{align}
  \begin{split}
      a & = b + c - d \\
        & \quad + e - f
  \end{split} \\
  g + h & = i
\end{align}