I’ve been using this inform-mode for Emacs, but the syntax highlighting isn’t that great, 'cause it’s not feasible for it to be great for the reasons @Natrium729 gave.
It occurs to me that if someone committed to some voluntary set of conventions regarding naming, for instance, that object names always began with ' and never had spaces, they could customize their syntax highlighter to respect those conventions and get improved results personally… but I don’t think any two people are likely to agree on the scheme, so it would continue to be a personal thing.