Meld has a line wrap option.
How do I tell it to keep words whole?
A few more small things:
Is there a way to change the keyboard shortcuts?
Undo undoes one character at the time. That's not a common behavior.
Can I change the whole color scheme and not just what I pointed out here: Meld: Change color scheme
Since Meld is currently my default tool, it means that the authors did a good job. However, since merging involves text editing, I think they should have started from a conventional editor rather than writing one from scratch.