Geekery question

[lightcastle]

The infamous confession post of doom presented me with the following as the origin of using "+1" to agree in comment threads. The argument is that it came from technical mailing lists and there was originally a longer code:

+1 = I support this idea.
+0 = I'd prefer this but I don't really care.
-0 = I'd rather not, but I don't care.
-1 = I oppose this idea.

Anyone know if it is true? My google-fu on such a subject is weak.