Pasting some plain text into the plain text editor seems to convert no-break space into normal space. At least the no-break space is not respected on word-wrapping and also when copying text out of the email is is copied as normal space. Given no-break space is a normal UTF-8 char and has its use cases this is not nice. Reproducible: Always
This seems to be no longer reproducible. Tested with help of LibreOffice (where Ctrl+Shift+Space renders no-break space). Copying and pasting between the composer and LibreOffice includes the no-break space, as intended.