I hate signature cards—that’s not a discussion. 
I’d disenchant them all for 0 dust if I could, but I can’t.
My question: If I use the option to Disenchant Extra Cards, would I lose the standard, golden, and/or diamond versions of any card I have a signature card of?
I’m afraid to use the feature anymore, because I don’t know what it’ll do. Anyone know?
They prioritize normal copies.
Basically normal cards die first.
A gold/signature/diamond card will only be dusted that way if you have extra dupes of that alternative version.
Iirc the mass disenchant will leave you with 2 copies of each version of a card
If you have 8 regular, 4 golden and a signature of the same card the mass disenchant will leave you with 2 regular, 2 golden and a signature
No, you can’t debate preferences because there’s no objectively correct answer.
I happen to dislike signature, diamond, and golden cards, too, but that doesn’t make me right in any sense.
That’s not true in the slightest. There are plenty of horribly wrong people in the world that “enjoy” bacon. They are free to be wrong about it all day long and that is their entitlement they can indeed, “enjoy”. But what is absolutely incorrect is that Bacon is enjoyable. Thats false as false can be. You can prefer Bacon or not Bacon. There is a correct preference and an incorrect one.
Hmm
Hmm hmm hmm hmm hmm hmm hmm hmm
Now that’s a fire!
Hmm hmm hmm hmm hmm hmm hmm hmm
Listen, son
Knock you in your head with my stick
With my stick
You gon’ have a mark from my stick
From my stick
My stick, my stick
My stick is better than bacon
Bacon, or do not bacon. There is no good bacon.
you don’t like bacon… hmm.
i kinda like it.
i guess i’m “incorrect” in your opinion
I can forgive you, not all who are lost are beyond redemption. 
I too hate signiture cards. They are ugly and having to hover over them to see what they do is annoying.
I have the very same issue with nearly all cards. It takes a very long time for me to be able to associate an image with specific actions or triggers or keywords. It isnt like driving, where a certain standard of shapes, colors, and symbols are utilized to convey info, but more like your vehicle’s fully lit up dashboard with all the variety of never seen before icons. I once had this symbol appear and I could only deduce that my vehicle could detect witches nearby because of the the cauldron it was showing me.
https://1.bp.blogspot.com/-ZNH9E__xmnY/Uowad2plArI/AAAAAAAAA3k/-TjLMJyjoz4/s1600/maxresdefault.jpg
Turns out that is supposed to mean its a Low Tire Pressure warning. After some reading up on it its a view of the tire if you could cut it half and see it head on. (Because thats an immediately natural way to look at one) And the walls of it have gotten wider as well as rounder instead of the normally mostly vertical (tho still rounded) shape. I get it now, but man I dont see how anyone could gather anything tire related from the obvious Witches Cauldron it is shaped as.