I was pretty sure the admins had fixed things so that two backslashes worked to insert a new line in TeX, but it no longer seems to work. Or rather, it works in the preview page, but not in the final output.
Two backslashes: \begin{bmatrix}a&b\\c&d\end{bmatrix}
produces $$\begin{bmatrix}a&b\\c&d\end{bmatrix}$$
Three backslashes: \begin{bmatrix}a&b\\\c&d\end{bmatrix}
produces $$\begin{bmatrix}a&b\\\c&d\end{bmatrix}$$
Click "edit" to see the desired behaviour.
\{
and\}
on in-line equations as well. $\endgroup$align*
s. Maybe it's the stars. $\endgroup$