1. Will it get you a ticket, or worse, from law enforcement?
2. If a driver hits you, will any part of your equipment give them an excuse to say you're partly at fault for operating illegally?
For most middle-class cyclists in nice neighborhoods with moderately-illegal lighting, I suspect 2 is more of a concern than 1. If you fit the profile of someone the police would like an excuse to detain, a blue flashing light would be an obvious enough violation to hang a stop on.