To change the attribution line (reply_header) when replying to messages,
one has to "jump through hoops":

So far I have for Mozilla Thunderbird 1.5.X on Linux:

Edit -> Preferences -> Advanced -> General -> Config Editor...

In the Filter box, type

reply_header

then select mailnews.reply_header_type and set its value to 3

I had also tried the QuickQuote extension which was not found when
searching the Thunderbird extensions page, but that appeared not to work
even after the obligatory restart of Mozilla Thunderbird.

What I still want to do is to have full control of the date format, use
of day-of-week and email-address in addition to user name.

This is just too difficult compared to the old days of using tin for
newsgroups and elm (or pine) for email.

Still, that wasn't enough. I further had to:

to set the date format that you want, you need to use the en-DK locale
to define your LC_TIME environment variable.

The following links were informative for me.

http://kb.mozillazine.org/Date_display_format
http://myy.helia.fi/~karte/international_iso-8601_date_on_thunderbird.html

I ended up putting a script in /usr/local/bin for thunderbird with:

#!/bin/sh
#
# ISO 8601 Date extension to Mozilla Thunderbird
#  must have the locale generated via
#   dpkg-reconfigure locales
#
export LC_TIME=en_DK.utf8
/usr/bin/thunderbird


If you are missing the locale, you'll need to generate using:

dpkg-reconfigure locales

as root.


[end quote]

Don't forget a couple of other "obvious" things:

chmod +x /usr/local/bin/thunderbird

If running KDE, edit the K menu entry for Thunderbird to use the path
/usr/local/bin/thunderbird

Arthur.