This interesting post about differential measurements with a scope has raised a few questions in my mind.

I have read about true differential scope probes and they seem to be very expensive. Would two high-voltage 1:100 probes with the following derating curve still be safe/suitable to perform A-B differential voltage measurements on mains-connected appliances?

If the ground alligator clips cannot be removed from the probes during the measurement, would clipping them together adversely affect the measurement? What about safety and accuracy of differential measurements at the frequencies at which switchmode power supplies operate (10Khz - 1MHz)? Apart from common mode noise, is there anything else that could affect measurement accuracy?