StackShare uses Markdown
We’re using Markdown parsers for Reviews, Blog Posts, and Stack Description (the text you’re reading right now). We’re using Bootstrap Markdown for content input (except for reviews) and RedCarpet for rendering in certain places.
WingTangWong uses Markdown
Markdown represents a highly portable and lightweight text formatting. I had converted all of my Wordpress posts to Markdown prior to migrating over to Jekyll and eventually to Hugo. The fact that many generators support Markdown means that my content remains portable regardless of the platform/engine I use.
v0lkan uses Markdown
What you see is not what you get, never it is.
Documentation is better in Markdown format. You don’t need anything special to read it.
It is compact, portable, comparable.
Markdown is my text file format of choice.
jflynn33 uses Markdown
Because it is almost an effortless markup language without ever having to write an HTML tag. Of course, you'll want to use it in environments that make it look pretty (GitHub, etc.)