I'm bringing up this issue again because I see a trend here.
What exactly do different quoting methods achieve?
[quoting is the process of including the original message in your reply with some form of "quote" character, like > for example marking the text as quoted, and a reply lead in like "On someday, someone said:"]
When replying to a mail, one has several options, viz. - don't quote the original - quote the original with the reply at the top - quote the original with the reply at the bottom - quote the original with the reply interleaved with the original
we shall call these "unquoted", "top posted", "bottom posted" and "interleave posted" respectively.
Let's look at the effect each of these has on persons entering late into the conversational thread, casual readers, and those who browse through the mailing list archives, and search engine to find results.
* Unquoted replies
This definitely is the most space efficient in that it includes 0 unoriginal bytes.
On the downside however, there is also a very high percentage loss of context (100% if the original mail had a stupid subject line like "Help me!"). What this means is that anyone entering the conversational thread late - in this case even one mail into the conversation, has very little idea of what's going on. Answers are no use without the right questions to go with them.
Mailers can aid in creating context for the user through threading based on the In-Reply-To mail header. The problem with this is that it requires that anyone who wants to read the thread should have all messages in the thread in his mailbox. People joining in late will not have all messages, they will only have the latest one.
It should be clear that, unless the subject line is all the context that's required, unquoted replies are very rarely a good idea.
* Top posted replies
It is common practice, and, in many cases, a good idea, to top post when replying to one-to-one personal or business mails. In these cases, the conversation is between two persons, and both have complete knowledge of all mails that have been exchanged between them. In such a scenario, unquoted replies would be a good option.
The average business/personal email user, however, receives a large quantity of email every day, and it may not always be possible to keep track of all conversational threads. Including context at the bottom for reference is therefore necessary.
This works only with one-to-one mails however. The moment we move to a mailing list/large group of recipients, this becomes infeasible.
It has been noticed that everyone who quotes the original below their reply quotes it in entirety. After having been through three levels of top posting, the size of the mail increases heavily with less than 20% original content (original content is that content created by the current composer).
Furthermore, the mail also gets cluttered with several long signatures which add no information to the thread.
It seems that when the original is below the reply, care is not taken to check the nature of the content quoted.
A second problem with top posting occurs when people join the thread late. Even though context is included in the mail, it is included in reverse order, which means that the mail needs to be read from the bottom up. This is not normal, since most people read from the top down. As a result, one needs to store context in ones mind while reading downwards.
Some of the worst cases of top posting are when people reply to a very long thread with a one line or even a one word answer, eg, "Thank you", "Yes, me too", etc.
Most people wouldn't delete the entire thread from below simply because they do not know how long it is - it would be completely hidden below the bottom boundary of their viewing area (window).
* Bottom posted replies
Replies posted completely at the bottom are only useful when the original mail is only a few lines long. Anything longer than that, and the reply ends up going below the initially visible area of the screen - for normal 80x25 screens/windows, requiring the user to scroll before he can read the reply.
The problem is further compounded when signatures are included in the quoted text. At times it isn't clear whether a reply to the mail exists, or whether the mail was simply forwarded completely quoted.
As with top posting, one liner replies are very hard to find at the bottom of a long (>15 lines) message.
A variation of this form of quoting is where the reply is included below the message, while all signatures are left below the reply. This serves the added purpose of increasing the cruft at the bottom of the thread.
* Interleave posted replies
In this case, replies are interleaved with the original message, so for instance, a message that contains three points, would have the reply split into three portions, each included immediately after the relevant point.
In this case, the person replying must take the effort to separate out points, deleting irrelevant lines, and in some cases summarising ideas. It is perhaps for this reason that most people choose not to employ this method.
On the plus side, anyone joining the thread late, or reading a single message on the mailing list archives will have the entire thread in front of him, with each question answered immediately below. Trimming of content helps keep the signal to noise ratio (S/N) high.
Interleaving is most useful when used in conjunction with trimming of content and summarisation.
The variation found with bottom posted replies is also found with interleaved replies, and reduces the S/N ratio somewhat.
* Closing remarks
This article isn't meant to tell people what quoting style they should use, but merely to state the pros and cons (according to me at least) of each method. You may choose for yourself.
I've tried to cover all points that have been brought up in the past. If I've missed anything out, feel free to add to this. I have not, however, gone deeply into the details, but the reader may refer to the list of links later on in this message.
Also note that this is *not* a poll. I am not soliciting comments on which quoting style is better.
* Further reading
http://www.cs.tut.fi/~jkorpela/usenet/brox.html to the point
http://www.blakjak.demon.co.uk/gey_stv0.htm excuse the background colour
http://www.blakjak.demon.co.uk/gey_chr0.htm top posting and blind users (and yes, excuse the background colour)
http://mailformat.dan.info/quoting/top-posting.html talks about top posting
http://mailformat.dan.info/quoting/bottom-posting.html and bottom posting
http://www.caliburn.nl/topposting.html perhaps a little fanatical, but a few good points
Also check google for "quoting mail and news"