As the question states, does anyone know of a style guide on how to represent different kinds of objects in ascii for documentation? By objects I mean things like boxes, networks, axes... anything like that.
What if you used whatever diagramming style best fits the domain you're working in, then used one of the following sites to convert the image to ASCII:
jave.de/
aa-project.sourceforge.net/aalib
I use asciiflow.com all the time for making quick tables or ncurses mockups to copypasta via messaging.