"Sometimes it may be better or easier to just isolate the test equipment from the ground and not the unit under test. "

"Floating the scope" is not good practice and may be illegal in a commercial setting. I do it but I am the type who works on live wiring and all that, there is specific and unmitigable set of rules for that which I will not attempt to list here. You have to REALLY know HOW to respect electricity, ESPECIALLY with tube equipment.

Pretty sure all scope manufacturers advise against it, some might try to void the warranty, maybe. Thee are other dangers, such as any ground fault in the test equipment you float can damage the DUT.

It most certainly can create insidious shock hazards as well, not just the ground and metal case of the scope, but ANY and ALL other test equipment connected to the same circuit(s).

I'll do it but I do not recommend it. Save that for when you have no choice..