Do we know why it was modified? I think hackernews stripped off the .md for some reason, but if you submit the URL with an anchor like https://write.as/hash.md#title that seems to preserve it
It was probably submitted incorrectly, my guess
When I tried to resubmit the correct URL, it was stripped again. Does it work for you?
didn't try myself, but looks like the URL has been corrected now! :D