Plain text is useful, but getting it in that form is trivial—it's just a textarea (nothing fancy like contenteditable, so it's already in plain text) and every

Plain text is useful, but getting it in that form is trivial—it's just a textarea (nothing fancy like contenteditable, so it's already in plain text) and every system that you could expect to use this from should have a functioning clipboard. A note with the look and feel of temporarynote.com calls for coordination from the author to modify their app to be able to output itself as a self-contained file.