Re: Do you use dinghy lights?
Good old fashioned common sense surely comes into it, albeit not in a legal sense.
Personally I think its simply silly to motor at speed, no matter what size of craft, without lights. Equally so to row across a channel unlit. Nevertheless rowing or motoring slowly from shore through a field of anchored or moored boats doesn't seem to pose a major risk presuming you have a light handy in case of the unexpected.
“Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life.” Terry Pratchett