Why does a greater-than sign (>) (not invariably but) often appear before the word "from" in e-messages and sometimes in other online text? Is "from" some sort of code word that has to be neutralized somehow (although I have no reason to believe anybody consciously inserts the >) lest it trigger some sort of response?

On my email program the '>' is automatically put in at the beginning of every line if the message has been forwarded. Includes in the top of the text who the forwarded message was sent to that sent it to you.

ETA: I just tested it, the version I have now at work puts a blue line at the beginning of every line for a forward. What I have at home and when I forward or reply from my Blackberry still puts the '>' in.

I certainly know about > or other symbol in front of a line indicating that this is part of the message being replied to. What I'm saying is that very often it appears (ETA 06.06) in body text (not just in the "from" line) in front of "from", and never in front of any other word, and I'm wondering what the explanation is for that. ETA some more 06.06: I don't see it as often as I used to but I did see it the other day; maybe some older e-mail programs (Prof. x uses PINE) automatically inserted the > while newer ones don't need to?