As a stylistic work around, you can use headings and thematic breaks (horizontal lines) to define clear sections for deep/shallow answers like so:
This is a quick, to the point explaination. It's at the top so people see it before the potentially overwhelming part to avoid "tl;dr". It can also be useful to get the high-level overview before diving into the details even for people who want to read them.
In Depth explaination
Here's the part with lots of quotes, tiny details, formulas and whathaveyous. The horizontal bar and heading clearly separate it from the simpler explaination.
You can add headings by placing # before the text on a line and three --- on one line to make thematic breaks, or you can use the editing icons to insert them automatically. You can also make sub-headings by varying the number of #s before a line to make big headings for short/long sections, but you can keep subheadings for the longer explanation if the need arises.
I prefer this to spoiler text as spoilers aren't as discoverable and it's harder to edit a spoiler well. Plus they reduce contrast a bit due to the block quote style that's applied to them.