FIST's place in the sort of unfiction and modern horror you see in the works of Remedy Game Studios or SIGNALIS is a really cool part of its design that makes it stand out as more than just an "Espionage Game." SYMBOL codifies that stuff in plain, clear english from the perspective of GM advice as opposed to a "setting book." The naturalistic language at use here is really good for FIST's improvisational, light roleplaying ruleset. New traits and roles related to the new theme is a CLASSIC move that I think every splatbook in FIST should do. I'm kicking myself not doing it in my own submission!
I find the aesthetic to be a double-edged sword: the plain word document style is extremely readable and usable and something as complex as memetic science fiction needs that clarity, but at the same time I feel like games about the conveyance of information could, very thematically, have cooler conveyance. I think that that's the number one place one could improve this project post-Jam and I think it's an excellent decision to get the text out the door before any aesthetics. Could you imagine taking on-site photography related to your project despite a looming deadline?? You'd have to be some kind of idiot, hahaha!
I'm not sure about some of the rules--cognitive therapy seems to take quite a long time, especially with more virulent memes, but it's an easily fixed rule you can play with, not something that the game is built on or that will have knock-on effects from changing. The COGNITOHAZARDOUS trait could use some better rules about how badly your DISRUPT should mess people up, but referring to other damage-dealing Traits is a good way to math out an ideal way to mess someone up that perceives you in the meantime.
Overall a really cool expansion with a lot of promise and excellent execution on a complex idea.