is it safe to have hot wire connected to ground (metal case, shield) via a capacitor?
I think this may be related.

EMI shielding
Look at C2/C3. This is a capacitive voltage divider that indeed will make your computer's case carry a voltage of approximately half the line voltage when not connected to ground. When your computer is not grounded and you touch the case you may feel the tingling and it should not reach a dangerous level. The two capacitors are there to improve the casing's performance for high frequency shielding (which a power supply like this as a lot of), so you mustn't remove them.
Safety ground
The other reason for the casing to be connected to ground is the fact that the entire case is made of metal and is easy to touch. Whenever some components fail or a wire comes loose, the entire case may carry line voltage and that can be leathal. When connected to ground, either the internal fuse will blow or an GCFI (Ground Fault Circuit Interruptor) in your home will trip.

As suggested in the link try using a multimeter to get the voltage of your case.

Connect a wire from the case of your computer to a cold water pipe or an 8 foot rod (made of copper or conductive metal) driven into the ground.
If you are feeling a tingle when you touch the case, that is a Bad Thing, and very unsafe.