Any way to stop Apple Mail from deleting a whole line every time I paste?

It's SO FRUSTRATING. Every time I paste some text in a Mail message I
lose a line below. WTF is Mail doing this? Can it be turned off? What
were Apple thinking? Text Edit doesn't behave this way. No rational
editor I've ever used does this.

TIA,
 Jamie Kahn Genet

-- 
If you're not part of the solution, you're part of the precipitate.