I need to pick between A and B but I can't hear a difference is the worst type of thread.

Maybe they are soliciting advice on what to listen for between the two specific components, in the normally vague audiophile language of course. Sometimes you just can’t find Waldo on your own until someone points him out. Then it’s obvious. Even if they really are sonically practically indistinguishable there might be service issues, compatibility issues, reliability issues, or price considerations.

it’s usually not about you. But I’m sure if you ask nicely someone can line up a barrage of asshat questions specifically directed at you. 

To me, I get kind of a kick out of it when a person that can't hear a difference between a couple of components asks this august body which of the two to buy.  I mean, the answer is easy.   Buy the cheaper one!

If I were to seek what might be earnest in this kind of question, it would be when someone is asking what other people have noticed which they might have missed. Once the quality is named, it is easier to notice. 

This has happened to me in audio, and also in wine tasting, in food tasting, in art. I think I've seen or experienced all I could and someone says, "Did you notice the dill?" or "Do you see there's bare canvas as part of the painting's color palette?" etc. 

It's weird to think that perception often requires training, but it does.

That, at least, is the best spin I can put on the question you're skewering.

It is an annoying question, as there is an obvious answer that every audiophile should know, at least every audiophile who reads The Absolute Sound: Get the more expensive one.

+1 mike_in_nc

More $ = better sound.   A freakin' no brainer.