I don’t know how many people have given the gmail settings more then a cursory glance but I was poking around before and found an option for personal level indicators. This little feature puts little arrows in front of your emails. One arrow denotes that your email address is specifically listed as a recipient among many and two arrows shows that you are the sole recipient of the email. This makes filtering email at a glance much easier and pulls attention away from any spam or list serves that might not be immediately important.
It’s a really small flourish that I wonder why it’s not turned on by default. Perhaps they make people turn it on just so they know what the little icons are. I didn’t notice this feature until recently and I never read about it any where so hopefully I’m not the last to know.