I'm not sure what symbols are you hinting at. First I thought it was to Fraktur kind of letters, but obviously this shouldn't be the case, as you point "teachin

I'm not sure what symbols are you hinting at. First I thought it was to Fraktur kind of letters, but obviously this shouldn't be the case, as you point "teaching" as a plus of redesigning them, and Fraktur symbols are used "traditionally" in relatively high level algebra (for some reason some symbols are used more in some realms, for me Fraktur started appearing when talking about complex stuff about ideals). Once you get used to them, it's like a second language, and that's it. I remember reading Feynman used his own symbols for sin, cos and other basic functions (turning them to one-stroke symbols) but he had to give up once he had to talk with other people. Math symbols are more or less a universal language. Once you know how the symbol appeared, or get used to "reading it right" they are totally natural. I don't see ∂ as a "weird d," I read this as "partial." It wasn't natural at first, but I got used to it, just like I got used to English.