dabbrev-eliminate-newlines

[Stephen Berman]

If you have a buffer with this text: 
------8<------
First.  Second.
------>8------
and later in the buffer type `M-/ SPC M-/', Emacs (started with -Q)
inserts this:
------8<------
First. Second
------>8------

It was only by stepping through Dabbrev expansion with Edebug that I
learned that this behavior is due to dabbrev-eliminate-newlines, in
particular that it is t by default.  Before that I wasn't even aware of
this variable.  I think at the very least dabbrev-eliminate-newlines
should be documented in (emacs)Dabbrev Customization, and its doc string
should reflect the above behavior (currently it reads "*Non-nil means
dabbrev should not insert newlines.  Instead it converts them to
spaces.").  It might also be a good idea to go a step further and
separate the handling of newlines and spaces, letting them be
independently customizable.

Steve Berman