Markdown is good. I use it when working in the company since the format is ubiquitous. I do writing my blog posts with Markdown (Hugo for the curious).

But personally, or working with a bit more niche team, for writing personal documentation I prefer Asciidoc [0]. It has better syntax and have some nice functionalities like Table of Contents.

For personal notes, nothing can surpass Org Mode [1].

[0] asciidoc.org [1] orgmode.org