There is not much talk of driving in the NORMAL mode here. I usually stay in ECO and occasionally SPORT.

The ECO light goes on in the NORMAL mode (as well as the ECO mode), as compared to never in the SPORT mode.

I was wondering if driving in the NORMAL mode can be as fuel efficient as the ECO mode, if you are gentle and try to keep the
ECO light lite. The major advantage of keeping it in the NORMAL mode would be to get some better response on demand.

The ECO light is pretty much entirely based on your estimated fuel economy. If it reaches a specified threshold, the light will illuminate.

This is expected behavior. Details are in the Owner's Manual. This can be disabled in the Vehicle Settings.

^Yes. The ECO light is dependent on throttle input, not anticipated fuel consumption. Similar thing but important to get it right.

Any mode can be as efficient as any mode, but eco mode encourages better fuel economy because it makes you work harder to achieve the same acceleration (more pedal input required)

It's really an encourager mode. "Hey friend lets take it easy here"

I believe it does mess w/ the ac to help you consume less fuel as well.

ECO light is just a feature to show you how to control your peddle. it's nothing more than that. If you're in sport, it's obvious that you wouldn't want to "light foot" your peddle. then what's the purpose of ECO light?
Many other cars have eco lights too. Honda has a green/blue/red gauge around it's gauge cluster.

No, it will not work in Sport mode at all. (Even the "Eco Indicator" goes dark when you are in Sport.)