indent), there derived a practice of included text being indented by
one ASCII TAB (0001001) character, which under Unix and many other
environments gives the appearance of an 8-space indent.

Early mail and netnews readers had no facility for including messages
this way, so people had to paste in copy manually. BSD Mail(1) was the
first message agent to support inclusion, and early Usenetters
emulated its style. But the TAB character tended to push included text
too far to the right (especially in multiply nested inclusions),
leading to ugly wraparounds. After a brief period of confusion (during
which an inclusion leader consisting of three or four spaces became
established in EMACS and a few mailers), the use of leading > or >
became standard, perhaps owing to its use in ed(1) to display tabs
(alternatively, it may derive from the > that some early Unix mailers
used to quote lines starting with "From" in text, so they wouldn't
look like the beginnings of new message headers). Inclusions within
inclusions keep their > leaders, so the `nesting level' of a quotation
is visually apparent.

The practice of including text from the parent article when posting a
followup helped solve what had been a major nuisance on Usenet: the
fact that articles do not arrive at different sites in the same order.
Careless posters used to post articles that would begin with, or even
consist entirely of, "No, that's wrong" or "I agree" or the like. It
was hard to see who was responding to what. Consequently, around 1984,
new news-posting software evolved a facility to automatically include
the text of a previous article, marked with "> " or whatever the
poster chose. The poster was expected to delete all but the relevant
lines. The result has been that, now, careless posters post articles
containing the entire text of a preceding article, followed only by