This episode aired this past weekend where they updated a kitchen with a dishwasher, custom counter top with built-in sink, dishwasher and stove.

One thing they did was used pipe dope on the sealing surface of compression fittings.

What's your opinion on this?

And one no no: It looked like they used a BX connector rather than a NM-B connector for the range hood.

I saw that too and questioned it. Seems like it would defeat the principle of a compression fitting. Might have some merit if the original fitting was being reinstalled after being taken apart which is what may have been the situation with that dishwasher. I have also heard of applying teflon or oil lubricant on installation to assist with getting a fitting apart later if need be; perhaps that was the intent. Write 'em a questioning letter, maybe you'll get a t-shirt.

I will use plumber's grease.

Compression is a funky fitting anyway. In industry I was using Swagelok with a pre swaging tool. Loved the fittings.

One thing they did was used pipe dope on the sealing surface of compression fittings.

What's your opinion on this?
After the compression nut split on a angle stop and flooded a condo unit to the tune of $27,000.00 the manufacture, Brass Craft, sentb us a letter telling us that they would not honor the warranty if the ferules were coated with pipe dope. Seems the pipe compound swelled and cracked the compression nut.
Regards, Tom

That's a really good reason not to do it. Thanks, Tom.