If you Google for ∀ you'll get a explanation of what it means. Same for ∫. Specialized fields require specialized knowledge. Same goes for programming, especially subfields of it. Every company has their own brand of programming language, C++ at Microsoft isn't the same as C++ at Google or Redhat or Apple. A new employee at a job will take months to be oboarded because they have to learn the company's dialect. During that onboarding, they'll learn about new words and they'll also introduce new symbols if they have to.

What does that mean for code that is being developed out in the open? Does it raise the bar for entry? Arguably there's already a bar to entry, which is being able to read English and being able to program in the first place. That there are some parts of the code that say "here be dragons" to the uninitiated who haven't yet Googled the meaning of the unfamiliar words and symbols seems like an entirely reasonable state of the world. If it's sufficiently popular, an explanation article, like https://en.wikipedia.org/wiki/Fast_inverse_square_root can be made, or an entire site, like http://explainxkcd.com.

There will always be more things to know (just today I learned about thixomolding. The science behind that has its own set of symbols to pick up), some of it will just require additional learning in order to learn.