I have just completed the upgrade of Discourse forum software. One of the new features worth noting is added support for Math notation
Example 1. Fraction and square root
x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
It is written using $$ notation as follows:
$$
x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
$$
Example 2. Integral
\int_{-\infty}^{\infty} e^{-x^2}\,dx = \sqrt{\pi}
written as:
$$
\int_{-\infty}^{\infty} e^{-x^2}\,dx = \sqrt{\pi}
$$
Example 3. Matrix
A =
\begin{bmatrix}
1 & 2 & 3 \\
4 & 5 & 6 \\
7 & 8 & 9
\end{bmatrix}
written as:
$$
A =
\begin{bmatrix}
1 & 2 & 3 \\
4 & 5 & 6 \\
7 & 8 & 9
\end{bmatrix}
$$
Example 4. Piecewise function
f(x)=
\begin{cases}
x^2 & x \ge 0 \\
-x & x < 0
\end{cases}
writen as:
$$
f(x)=
\begin{cases}
x^2 & x \ge 0 \\
-x & x < 0
\end{cases}
$$
Example 5. Fourier series sum
f(x)=a_0+\sum_{n=1}^{\infty}
\left(
a_n\cos\frac{2\pi nx}{L}
+b_n\sin\frac{2\pi nx}{L}
\right)
written as:
$$
f(x)=a_0+\sum_{n=1}^{\infty}
\left(
a_n\cos\frac{2\pi nx}{L}
+b_n\sin\frac{2\pi nx}{L}
\right)
$$
More info / documentation here: Discourse Math - Plugin - Discourse Meta
