More is NOT better. I can't find the exact Rule, but it is not permitted to show more than one set of sidelights at the same time. You could have 2 sets of sidelights on seperate switches, so that you could use the combination red/green OR the seperate sidelights, but NOT BOTH. I do know that if a USCGAUX or USPS Vessel Examiner is checking a boat during a Vessel Safety Check and they find double lights (both coming on at once) they can not issue a Decal to that vessel, and since the VSC follows USCG and state regulations it would indicate that there is a Federal rule against displaying both sets of sidelights.
It is amazing how careless many boaters (and sadly some manufacturers!) are about NavLights, many powerboats are running around without their masthead light since it "causes too much glare" to the person at the helm, or else one or more of the lights are blocked by a RADAR antenna or searchlight or the dinghy is pulled up on hte transom blocking the sternlight. Sailers are not perfect either, those tricolor NavLights used by some at the masthead are to be used ONLY under sail, yet I've seen sailboats using them under power. Also, if the Tricolor is turned on, the deck level NavLights should be turned off. It is allowed to use 2 360deg lights at the masthead (top one red, with green under it) in addition to the deck level NavLights, but again...ONLY when under sail. As soon as the engine is started, the Steaming light should be turned on (and the tricolor or other masthead sailing lights turned off) and the boat is now considered a powerboat under the rules.
From a practical standpoint, the more lights you have on, the more precious battery power you consume. So, that is another incentive to display ONLY the proper NavLights. That guy with the red sternlight would sure cause confusion! I'd wonder how he could be moving "sideways"!
On the subject of boats with the red/green light reversed, it is unfortunately and easy mistake with some light fixtures (lens was installed upside down), no excuse for this, but it happens. One sailboat builder who I will not name, actually shipped boats from the factory for at least part of a year with the combination light on the bow pulpit upside down.....red was showing to starboard, green to port. They did fix the boats (turned the lens over) but it was embarrassing! Just remember....Red, Port, Wine (aka, red light shows to port)