Why not [compute a z-score]?

Well, obviously you can compute it. But you shouldn't call it "z", you should call it "t" :-).

Well, that basically never happens.

Indeed. (That was the point of about 1/3 of what I wrote.)

it's a complicated process

No shit :-). But the point is, it's a more complicated process than the one Jacob seems to have been envisaging, where you do a statistical test, find that your results aren't significant at whatever level you chose, and give up. (And of course more complicated again than the one that on the face of it he's criticizing, where you do a statistical test, get it wrong, think your results are significant, and immediately decide to use them.) So when Jacob says (I paraphrase) "you need to correct your results for multiple comparisons, so they won't be significant any more, so they're useless", he's not necessarily correct. What you have may be hundreds of results that all fall well short of statistical significance (when you test them right) because you've got such noisy and complicated data, and the task is to make the best you can of them.

That's a horrible idea.

That was kinda my point :-).