This is because they didn't mark their code as "code", and a `#` at the beginning of the line is a markup for

#Inappropriately large headings

I don't think most people use the `#` functionality, because 1) I don't think they know it exists, and 2) It looks dicky (what's wrong with **bold** for headings?)

Anyway, if you see that, you can edit the text and code-format it (or wrap it in `<pre>` tags) and it's all good.