Sure. I'm not sure all the patterns that are not supported but here are three which I have stumbled on.
The following 3 chunks work fine in MathJax:
## scaled division lines
$$
x = a_0 + \cfrac{1}{a_1
+ \cfrac{1}{a_2
+ \cfrac{1}{a_3 + \cfrac{1}{a_4} } } }
$$
## scaled text
$$
( \big( \Big( \bigg( \Bigg(
$$
## matrix fonts don't scale
$$
M = \begin{bmatrix}
\frac{5}{6} & \frac{1}{6} & 0 \\[0.3em]
\frac{5}{6} & 0 & \frac{1}{6} \\[0.3em]
0 & \frac{5}{6} & \frac{1}{6}
\end{bmatrix}
$$
Those equation blocks look good here in MathJax or LaTeX:
scaled division lines
x = a_0 + \cfrac{1}{a_1
+ \cfrac{1}{a_2
+ \cfrac{1}{a_3 + \cfrac{1}{a_4} } } }
scaled text
( \big( \Big( \bigg( \Bigg(
matrix fonts don't scale
M = \begin{bmatrix}
\frac{5}{6} & \frac{1}{6} & 0 \\[0.3em]
\frac{5}{6} & 0 & \frac{1}{6} \\[0.3em]
0 & \frac{5}{6} & \frac{1}{6}
\end{bmatrix}
But they look like this in MS Word/PowerPoint:
It seems the second two formulas reflect that MS Equations don't support font scaling inside the equation. And both of those need some fonts inside the eq to be different in order to look right. The top chunk may be an equation syntax issues, although I have no idea what it is. It renders fine in MathJax & LaTeX but gives me this when rendering to MSFT products:
[WARNING] Could not convert TeX math '
x = a_0 + \cfrac{1}{a_1
+ \cfrac{1}{a_2
+ \cfrac{1}{a_3 + \cfrac{1}{a_4} } } }
', rendering as TeX:
^
unexpected "{"
expecting "%", "\\label", "\\nonumber" or whitespace