So, just how would the emergency exits get opened when the aircraft is on
the ground and needs to be evacuated, if the cabin pressure is significantly
higher than the outside pressure?

I'm guessing that the pressure differential at ground level isn't enough to
prevent the exits from opening, but that this differential is (logically)
much higher at altitude, and thus would prevent the exits from opening in
flight. But I could be wrong.

And yes, sadly the whole newsgroup thing is a never-ending disappointment.
The most humorous recent example came from the "gun loons" thread, where I
suspect that 5 or 6 people are STILL arguing about the difference between a
"box cutter" and a "carpet knife".