What is a line? continued

My previous post was focused on graffiti mark making. As the quote I am responding to is "A mark indicating connection, boundaries or postion" , I wanted to also look into other uses of line, be in ancient, instructional or gestural. but all with a common clause, all these methods of mark making are seemingly relevant to social communication in some way.

Ancient Egyptian hieroglyphics are interesting to me because they are interpretations of language through iconic line Eg the papyrus leaf representing E or I. Hieroglyphics were presented to the educated masses in the same form graffiti is, so a tenuous link.
Line is also often communicated in the form of instructional information to make instructions clearer to us in a visual and often linear way, It is known most people respond better to visual instruction.
Musical notation is comprised of lines and dots, and runs across a line to document, where melodies fit into each other and  other things like tempo etc.
Road signs are in a way capitalist graffiti, you are forced to follow their rules. ANYWAY, they are also comprised of lines and most of the instructional qualities on the signs themselves are linear.
In the broader sense, I think all these methods of mark making, relative to communication are all similar to tagging, opinions of tagging aside for the moment, as for now I'm just looking at it for its linear qualities and how the lines connect, or dont connect in accordance for the artists personal and visual end result.