Although it’s preferred to interleave quotes on Usenet and “trim” all extraneous material (which is already accessible from the rest of the thread), “top posting” with a running full copy of the previous thread is actually the de facto standard for email, so “start my reply above the quote” should be the default for email accounts.

“Good. No, the answer is an orange and two lemons.”
“Lemons?”
“If I have three lemons and three oranges and I lose two oranges and a lemon, what do I have left?”
“Huh?”
“Okay, so you think that time flows that way, do you?”

-Mostly Harmless