I've finally added a nice little feature to the mathstodon.xyz web frontend: while you're typing, LaTeX math macros will be replaced with the corresponding unicode character. So I can write something like "the area of a circle of radius 3 is π × 3²" very easily! MathJax still works, between the delimiters: \( π \times 3^2 \)
This is based on the list of Unicode replacements from http://www.unicodeit.net/ by Sven Kreiss and Kyle Cranmer. I found myself switching off to unicodeit to get symbols, usually × and π, so often that I wanted to integrate it with the Mathstodon frontend.