I would fix other people's lines if they asked me on occasion. The hard part of writing is the architecture of it, getting the story and structuring it. Not the tweaking of lines.
It would have been nice for Greg to eventually grow into a mature relationship with Laura. He was moving toward that already but then took a turn into the juvenile with Paige.
David was the kind of guy who was totally supportive of the actors and instructed the writing staff to trust the actor's instincts, since after all, it's the actors playing the character.