Earlier quoted context omitted.
Most people don't write file paths. Only a concern for programmers, who should be fine escaping them by whatever mechanism.
Most people don’t write markdown! What’s the demographic of markdown writers who don’t write file paths? Bloggers?
I will say that forward slashes are still more common in regular english text even among non-programmers than underscores. For example, listing options a/b/c.
And you know, URLs.