I recently ran across a post on Jay Fields' blog, in which Jay uses emacs' font-lock mode to change the display of words into symbols.
Is there any way to do this in Vim?
Yes, Vim's conceal feature replaces matches with a single replacement character (or none at all). This is integrated into syntax highlighting, see :help :syn-conceal
.
For example, the built-in Tex filetype uses this to display special sequences directly as Greek characters etc.; see :help tex-conceal
. The implementation is in runtime/syntax/tex.vim
in the standard vim distribution.