__mean =: +/ % #
Becomes: mean =: +/ % #
Don't use the surrounding ```...``` because it just becomes noise, and you don't need extra newlines, two lines of code can be adjacent to each other if you prefix each with two spaces: line 1
line 2, no extra newline was used
https://news.ycombinator.com/formatdoc - a very short document describing all the formatting options for HN comments. There aren't many.