Most modes that use custom fontification (ex occur-mode), won't turn the font-lock-mode off. So hi-lock would add a keyword, and remove all existing fontification. The below patch fixes this behaviour.

Evgeni

Modified lisp/hi-lock.el

diff --git a/lisp/hi-lock.el b/lisp/hi-lock.el

index e2dc4ea..e16ed76 100644

--- a/lisp/hi-lock.el

+++ b/lisp/hi-lock.el

@@ -689,7 +689,7 @@ Otherwise, read face name from minibuffer with completion and history."

;; Refuse to highlight a text that is already highlighted.

(unless (assoc regexp hi-lock-interactive-patterns)

(push pattern hi-lock-interactive-patterns)

- (if font-lock-mode

+ (if (and font-lock-mode (font-lock-specified-p major-mode))

(progn

(font-lock-add-keywords nil (list pattern) t)

(font-lock-fontify-buffer))