I had been resorting to using 3rd-party tools in order to improve the reply and signature handling in Novell GroupWise.
I recently gave vanilla GroupWise 7.02 a try. The signature had an empty line in it - here is how to remove the line ...
Disclaimer: As with everything else at Cool Solutions, this content is definitely not supported by Novell (so don't even think of calling Support if you try something and it blows up).
It was contributed by a community member and is published "as is." It seems to have worked for at least one person, and might work for you. But please be sure to test, test, test before you do anything drastic with it.