You should in theory fold it back and forth, not coil it, as a coil is making an inductor, which can change the loading on the amp and the sound........
Note the forth word was "Theory" ..... Whether you hear a difference depends on many factors, level of Kit, type of insulation around the cable, it's construction.... bla bla bla..... and the fact someone suggested on the 'tinternet !!!!
Simple solution fold it and don't worry about it.