When rendering small text, TMPro can be a little aggressive when cropping quads, resulting in ugly thin lines at the edges of some characters:
Here the l in bagel really ought to have another pixel of width, but TMPro crops it too aggressively.
This can be worked around by adding a small amount of softening and a small amount of fully transparent outline:
This tricks TMPro into making the polygons an extra pixel or two across, which creates a much more pleasing result:
However, this comes at the expense of crispness when fonts are rendered very large. I would post a picture but 5 is the limit.
What I ended up doing was hacking the shader (in this case the mobile version) as follows:
float hackout = _OutlineWidth + (0.121*(min(20.0pixelSize.x, 1.0) - 1.0));
float hacksoft = _OutlineSoftness + (0.078(min(20.0*pixelSize.x, 1.0) - 1.0));
scale /= 1 + (hacksoft * _ScaleRatioA * scale);
float bias = (0.5 - weight) * scale - 0.5;
float outline = hackout * _ScaleRatioA * 0.5 * scale;
The upshot is that when zoomed in a lot, the shader code above ‘undoes’ the little bit of softening and outline set in the material, but leaves it in place when the text is small on-screen.
Hope that’s some use for someone 
