I remember when I was vectorizing flags (the simple geometric kind, though, since I've done it with a text editor and some scripting/templating) on Wikimedia Commons as a pastime years ago. I got reasonably well-versed in parsing heraldry as a side-effect and it was fun in a way, considering that it is indeed a fairly precise description syntax for coat of arms and flags.

And I got confused when GRRM started using proper heraldic descriptions for flags in ASoIaF with the third book, while the two before were basically just very simple English descriptions. Most readers probably never really noticed :)