One of the WoW 4.x patches broke the method Levelator used to add level tags to quest titles. (Or rather, made it impossible to use said method without causing “taint” and “blocked action” errors.) I could rewrite it to use a different method, but then it’d be nearly identical to half a dozen other quest level mods, and I see little point in duplicating them.
Besides, Blizzard already supports quest level tags in the default UI… it’s part of Colorblind Mode. (Though it’d sure be nice if they let you turn quest levels on without getting all the other colorblind options, too.)
I’d recommend those seeking an alternative check out Tekkub’s Quel’evel.