The man page has claimed a '--version' command-line argument since 8c4801bb (Man page by Eike Sauer, 2004-01-20), but I get:
$ kdiff3 --version Unknown option: --version …
Ideally this version-check would work even without X, which is currently giving me:
$ DISPLAY= kdiff3 --version kdiff3: cannot connect to X server
Having a --version option would allow me to check the installed KDiff3 version programatically, which would be useful for testing student installations for up-to-date versions. However, if implementing a --version option is too much trouble, I'd at least like the option removed from the man page ;).