Good find, ML! I'll read this more carefully later. In the meantime, you absolutely should test the ground quality in all your AC outlets -- even if you have no interest in "earthing!" You are wise to be cautious!
Any way, I bought this ground fault tester from Lowes for $8.00:
Amazon.com: Gardner Bender GFI-501A Ground Fault Receptacle Tester and Circuit Analyzer: Home Improvement
I found 3 bad plugs in my house. I am still trying the grounding thing, it's working for me.