I like this a lot and might even use it myself. That said, the link generated is much too long for sharing, esp on Twitter, but probably anywhere. I'm guessing its a known issue though.
If the url is less than 2000 characters, goo.gl (google's url shortner) will work, and that makes it much more sharable... but for bigger writings, I'm at a loss.
An export function would help here, but in the end, sharing from ZenPen.io would be preferable.
Open to any suggestions :)