I make substantial use of
prettify-symbols in my programming buffers. A snippet of some of my python symbols:
(add-hook 'python-mode-hook (lambda () (mapc (lambda (pair) (push pair prettify-symbols-alist)) '(("for" . ?∀) ("in" . ?∊) ("not in" . ?∉) ("return" . ?⟼)))))
This works fine for all cases except (html) exporting.
Pretty symbols from source code, or even directly from org-mode text, will not transfer over after exporting.