Summary

I don't know about other interfaces, but Repetier-Host is imprecise enough to label the original non manifold, so I just increased the block size to get around this.

Instructions

This is exactly like the original by pgreenland, only the size of the cubes used to construct the letters was increased.

    //Output cube      translate([icol + (6*itext), irow, 0])          cube([1.05,1.05,1]);

If the text still shows up as non-manifold, increase the x and y dimensions of the cube in the code above, found at the bottom of the drawtext module (scroll to the bottom of the scad and you'll find it).

If for some reason you need to make the text more defined, decrease the x and y dimensions of the cube, but make sure to keep them above 1.

Manifold text