Just took my reflectors off
Based on this, and some more Google searching of New York State laws, I removed my front & rear reflectors because I have reflective Schwalbe Marathon tires. Also I always, even in daytime, ride with lights (Serfas SL-200 in front, and a Blackburn Mars 2.0 or 3.0 (I have both) in rear).
Only saved 2.7 oz, but they're ugly little pieces, easy to remove.
Note: I'm not a lawyer, don't construe this as legal advice.
Oh, and I highly recommend a bell. A very unobtrusive way to let pedestrians (of which there are many in NYC) know that you're coming. I recommend Mirrycycle Incredibels. Clever Lever is a good one for Brompton because the lever is 360 degree adjustible. Cheap too. I've also used the Original.