Why am I finding all these undocumented functions (like COMET) in MATLAB?

Almost everything in the "demos" directory is not described in the User's Guide. There are lots of goodies there. In 4.0, the demos are best place to see examples of Handle Graphics. There are other undocumented functions in directories other than demos. Some of them are "worker" functions that are unlikely to be used directly; they are simply called by other functions. A few, like COMET and COMET3, were actually written after the User's Guide had been sent to the printer.