Just adding more information to what Dav999 said.
In say commands, the color parameter* is ignored and all text boxes will be gray and centered.
The commands map(on/off)* and squeak(on/off/crewmate/sad/...)* will be completely ignored, but I think that never causes level-breaking problems.
Say/reply commands with more than 5 lines will show internal scripting in the text box (instead of the text itself) in 2.0., but I think that doesn't make VVVVVV crash or anything.
*See more info at the "Script commands index and tips thread" in this board.