I've never seen the bleeder valve leak, nor have I ever had cause to loosen it. The system will prime itself without fiddling with the valve. I guess if you wanted to change the fluid you could bleed some out there.

What I have seen too many times to count is the case goes bad internally filling the case with fluid having it overflow out the top of the case near the bleeder valve. If your friend is adament then have him clean the valve area with solvent and compressed air and have him run it and show you the valve leaking. That will likely change his tune.