We have had a number of issues with some fonts where there are artifacts in the rendering of glyphs.

This thread for example: https://forum.playcanvas.com/t/how-to-display-cyrillic-and-glyphs-characters/18631/14

Is there any way we can increase the quality or have the user have some control about the resolution per glyph to allow for more complex fonts?

Some of the issues looks similar to what have been mentioned here: https://lambdacube3d.wordpress.com/2014/11/12/playing-around-with-font-rendering/