Hi ~plasmon, and welcome to the Midnight!
You can type your posts in Gemtext here, and it turns out that there is a way to post mathematical notation in this format. You just create a preformatted text section (surrounded by lines containing triple backticks as in Markdown), and then place ASCII-art rendered math formulas and plots inside it.
Here's an example:
pprint(Integral(sqrt((1+x)/(x**2+3)),x)+Sum(1/j**2,(j,1,n)))
n
____
⌠ ╲
⎮ ________ ╲ 1
⎮ ╱ x + 1 ╲ ──
⎮ ╱ ────── dx + ╱ 2
⎮ ╱ 2 ╱ j
⎮ ╲╱ x + 3 ╱
⌡ ‾‾‾‾
j = 1
plot(sin(x),(x,-2*pi,2*pi))
0.99830 | ... ...
| / \ / \
| / . / .
| . .
| . .
| . .
| . .
| . .
0.05872 | -------------.--------------------------.--------------
| . . . . /
| . .
| . .
| . .
| . .
| . .
| . / . /
| \ / \ /
-0.9983 | ... ...
-6.28319 0 6.28319