I don't mind getting behind somebody as long as it's daylight so that I can see them, and know when they are stopping and/or turning. I know how hard it can be to keep trailer lights working. However, some peole don't care. Common lore is that if you rear end somebody you are automatically at fault. I don't know how that works if they don't have taillights. A couple of years ago I came up behind a pickup pulling a contractor's trailer, so all that I saw was a white wall. Unbeknownst to me he was pulling in to get gas at the same place I was. As a courtesy I mentioned that his trailer lights were out. He already knew but didn't care. Had I been motoring through I probably would have smacked him doing about 40.You can clearly see the trucks lights. I have talked to police in rural North Carolina and Virginia ad they don't mind if the trailer does not have lights so long as you are driving during the day and can see the lights from the tow vehicle from behind.
Investigators can tell from the way the filaments are, whether your taillights were on. An officer may not go to that extent unless there was a fatality involved. If an insurance company is looking at a 6 figure settlement however, they might go the extra mile. My company truck has dash cams front and rear, making it easier to tell whether I messed up or if somebody else did.