So I race over to the Trek dealer on my lunch hour today. The first person I see is my friend the sales manager. The Domane is the fourth bike I've bought from him. Super cool dude, knows more about bicycles than anyone I know. I explain my concerns to him, and instead of looking at the bike, he points to the wall. "Take a look at the [Bontrager] RXL handlebars over there." Sure enough, they have the exact line in the exact same position as the one on my bars. The "crack" is merely the way the carbon fiber is laid during the manufacturing process.

Better safe than sorry, as the old cliche goes...