Thunderbird 45 Create New Message: default style is Paragraph instead of Body Text

For some unknown reason we got this change in v45.
If you want to go back to "Body Text":
Open the Options window, go to Composition -> General and uncheck: "When using paragraph format, the Enter key creates a new paragraph".
Which is kind of obscure since no one told Thunderbird to start using paragraph format in the first place.
But that does it, so...