If airfoils at low speed generate higher coefficient of lift, why is it not reflected in airfoil polars? If airfoils at low speed are able to generate a higher coefficient of lift, why is this not reflected in airfoil polars?

I understand airfoils generate a higher coefficient of lift at low Re numbers.

So I entered the NACA2312 airfoil in javafoil and generated a lift polar for the airfoil from Re 5,000 to 10 million. There was no increase in lift at lower Re numbers... 

Why not?
No, they don't.

The Reynolds number is the ratio of inertial to viscous forces in a fluid. That means viscosity has proportionally more effect at lower Reynolds numbers. The boundary layer is proportionally thicker, friction steals more energy from the flow and lift is lower.

This answer contains a graph with a collection of empirical data, as does this answer. Here is another answer which covers both attached and separated flow. As you can see, Reynolds number effects mainly affect attached flow, and in a way that reduces lift for the same angle of attack; the more so, the closer you come to the stall angle of attack.

Just to save you from following all the links: See below for a plot of the venerable NACA 4412 from Abbott and Doenhoffs collection of airfoil data (picture source):



Note that the lift coefficient is plotted for Reynolds numbers R of 3, 6 and 9 million.