[eru]

Send GET requests, delay POST.

Yes, the whole architecture would need to good undo-support.

[jfoster]

At this point it's a good idea to keep in mind the effort/gains ratio. You're proposing massive changes to JavaScript engines in order to have double tapping work a certain way. Changing the gesture or tweaking the delays might yield a less optimal solution, but the effort is so much closer to 0. If you were going to invest the effort you're proposing into something, would improving this delay be the best knowable use of that effort?

[andy_ppp]

You go down this road until you say to yourself... Ah next version, I'll just at a 350ms delay for now.

[untog]

A lot of sites out there perform actions on GET requests, though. I just don't see it working out.

In any case, once you start delaying things you ruin the original point of getting rid of the click delay - to make things faster!

[eru]

You only delay non-idempotent actions.