Top/bottom posting is partly an issue of taste, but mostly an issue of netiquette. And common sense.
because it breaks the flow of conversation.
The main reason you should NOT top post is...
But there are plenty of other good reasons [Why is Bottom-posting better than Top-posting]. Basically, remember that your email is written for someone ELSE to read, not you. Make it easy for the recipient to understand and reply to himself.
That also means not quoting the whoooole message in a reply. As a general rule, if the amount of quoted text in your email is more than your own text, you have probably quoted too much.
E-mail
is not a conversation. This whole mindset of e-mail being a "conversation" is what led to the creation of g-mail, the world's worst e-mail service. heh, and if you notice, g-mail even puts the most recent message at the top of the thread - or it tries to, I should say. Usually it starts a new thread like an annoying board troll. E-mail is not a "conversation". Think of it like sending electronic postcards back and forth. You may save all your postcards, but do you read all the previous ones before the one that came in the mail today? Maybe if you have a few screws loose, but most people would read the most recent postcard, then refer to the older ones as, when and if needed.
Having to scroll through previous quoted messages (which can sometimes be pages and pages in length) to get the signature of a message is just goofy, but I realize some people just have to be different, so whatever, I find it very annoying. The idea that I should scroll past all that crap to find the message as well is just plain goofy. Unless that e-mail was from a boss or someone important (i.e. someone who has something I want - i.e. a paying customer), I'd likely delete it rather than read it. Time is too precious to waste it on people who waste it intentionally by being petty.
And the link you rely on for support of your position is written by someone who does not know the difference between Usenet and E-Mail. They are NOT the same thing. Usenet is a conversation, e-mail is not. Netequitte is fine and dandy. Some of it has a purpose and a place (like NOT TYPING IN ALL CAPITAL LETTERS) but most of it is junk that people with way too much time on thier hands and who are way too willing to tell others what to do come up with.