I think the experience of annoyance would be very different if you are forced to "break your flow". E.g. if you need to correct some characters at the end or in

I think the experience of annoyance would be very different if you are forced to "break your flow". E.g. if you need to correct some characters at the end or insert something in the middle of what you have already typed because then the feedback is much more important. If I just keep typing typing typing without need to worry about correction, the annoyance is probably minimal. I could just ignore the latency, close my eyes, and keep typing, assuming I have really high touch-typing accuracy. (I know that's something I sometimes do when I face high latency in real usage.) Maybe a better and more meaningful simulation is to show some random sentences that you have to read and type, and then randomly force you to make some corrections as you go along (e.g. suddenly change the last word from "their" to "they're"), to simulate you having mistyped something.