Every mathematician who has ever exchanged (La)TeX files by email must have noticed lines starting
¿From…
appearing in the resulting dvi or pdf file.
These charmingly infuriating lines are due (if I understand things right) to TeX’s transforming the character “>” into the inverted question mark, and to the tendency of email programs to consider that a line starting with “From” means that an included email is starting, which must be quoted with “>”. Since mathematical papers tend to have sentences like “From this, it follows that…”, this is what we end up with, unless one is careful to regularly search the document for the telltale “>From” in order to remove the offending symbol (or one gets the reflex of cleverly writing “{}From” instead of “From”, something I just learnt from a coauthor.)
But I find it ironic that computers, which can apparently spell-check documents, correct their grammar, or attempt translating them into Esperanto, are unable to understand that sentences starting with “From” might be legitimate…
This is a quirk of the mbox format for storing many emails in a single file, which is the default for many common mail clients . The individual messages are demarcated by lines that start with “From” and hence any such lines in the message body have to be escaped, traditionally by adding a “>”. These escaped lines are usually decoded by the client, though as you’ve noticed, sometimes they persist when you save the files.
This quirk doesn’t affect TeX files sent as attachments, which I find easier anyway…
Thanks for the more detailed explanation!
I have the impression that sometimes, even sending the LateX files as attachments does not work, since I always do it in this way, and don’t remember having received one otherwise either in a long time, and yet I have noticed a “>From” appearing just within the last two days…
BTW, the quirk on the LaTeX side, for showing > as ¿, is because of using the deprecated (but default) OT1 font encoding instead of, say the T1 encoding. See the following questions on the new TeX questions website:
Less than symbol (<) appears as upside down ! and
Why should I use \usepackage[T1]{fontenc}?