NEW YORK — Though "The Dark Knight” has been a bona fide cultural event, boasting rave reviews and boffo box office, it hasn't been immune to criticism. Some have quibbled with its political undercurrents, and others have criticized a muddled theme.

But here's the critique most widely held: Why does Batman talk like the offspring of Clint Eastwood and a grizzly bear?

Donning the costume for the second ti...