About privacy & security
This editor is hidden behind #edit so Bawk won't stumble onto it, but it is not a lock. Anyone who adds #edit to the link can open it β although their changes only affect their own browser.
A password checked in JavaScript would not be secure either: the letter text is inside the page itself, so anyone with the link can read it with "View Source". For a truly private letter, protect the site with Cloudflare Access (free for small teams) so only Bawk's email can open it.