Should Harley Davidson heads be ported and polished?

The answer depends on what other modifications are performed on the engine. A completely stock engine with "ported & polished" heads might run worse than factory, depending on how much the ports are enlarged, what shape they are ported to, how smooth they are polished etc... To receive the benefit of a good port job, there needs to be a reason to do so, such as a larger (more lift) cam, larger carburetor (or larger throttle body), more compression (different pistons), or valve size (larger diameter or reduced stem size) etc.. This is true for any piston powered 4 stroke engine. Sorry to be vague, but this is a general question.