Like this.
> How?
>> Because it means the reader has to read the conversation backwards.
>>> Why not?
>>>> Because it doesn't make sense to put it above.
ZFR: Just out of curiosity, why would you say it's better to have your response below?
Now that I've got that out of the way...
ZFR: Assuming the quote was necessary in the first place, I find it easier in e-mails if I first read the response, then if I need more context, scroll down to see previous correspondance, rather than having to scroll through a previous email before finding what the guy wrote.
The point is that if the respondent sets out their reply correctly you won't need to scroll to find out what they wrote, because the bit they quote will be short enough not require any scrolling - it'll have just enough to make it clear what they're replying to, with the response readily visible immediately underneath. If they're replying to several different bits then each one will be quoted separately in turn, with the relevant response immediately underneath each bit.
Contrast the top-posting that has become the norm - having the reply at the top gives no indication of which bit of the previous message is being replied to, or even if the message being responded to is the immediately preceding one or an earlier one. And to read the earlier messages to get context, you need to scroll all the way to the bottom (i.e. start) of the reproduced e-mail chain, then scroll to the top of the first message, then scroll down as you read it, then scroll back up to the top of the second message, scroll down as you read that, scroll up to the top of the third message and so on. It means more awkward scrolling, not less.
Of course, it may be that the reply makes it obvious what is being responded to, or is just a general response rather than addressing a specific section of an earlier e-mail, so there is no need to quote a snippet immediately above it to provide context - but that's not an argument for top-posting, it's an argument for
not quoting the previous message(s) at all.