I’ve added the MathJax plugin to the forum site so it should be possible to add equations now. In-line equations \psi_0 =10^4 using the $ ... $ pairing and display equations with $$ ... $$
\nabla^4 \psi = \frac{g \rho \alpha}{\eta} \frac{\partial T}{\partial x}
See settings / plugins for options that can be changed. Source code is from here: https://github.com/discourse/discourse-math.git