I learned something new...plugging anything into the trailer wiring harness turns off blind spot monitoring. I checked the manual and this is intentional with no way to override it. In fact, you need to unplug, then restart the vehicle to have BSM function again.

I have a 1UP hitch bike rack with the 1UP LED taillight. Drivers here in the Boston area tailgate like NASCAR drafting, so a clearly visible brake light is a good idea. Just have to remember to double check side blind spots myself when changing lanes with the bike rack on.