Apparently Dr Fang himself did this mod to his own HE5LE several years ago and it's still working fine now. It's a Hifiman-original mod.
I would say this little mod is recommended but with discretion - if you use the cans exclusively in a clean, low air-flow, low-dust home or work environment, there is probably nothing to worry about. If the environment has some attributes that seem a bit icky (dusty, gusty, big temperature/humidity swings, sharp debris in air, etc) then just don't.
Edited by jerg - 7/16/13 at 9:50am