program statements were arranged in a sensible order, experts were able to remember them better than novices. When statements were shuffled, the experts’ superiority was reduced
My browser must have missed a couple paragraphs in the download. How do you get from this to tabs/spaces? I can see how putting things in the wrong order makes it harder, but I don’t see how that applies to what character code you use for pushing your statements to the right. With the right editor settings, you can’t even tell the difference just by looking.
Surely, even if I admit that one’s memorization skills are affected by their order (which I think is reasonable), I don’t see any reason to jump to the conclusion that they’re affected by something which is, by definition, invisible.
Do you also think it is harder to remember things about some source code if it uses different linefeed characters, or a different Unicode encoding, or is stored on a different filesystem? Because these things sound exactly as relevant to me.