@Hexagons, the advice from @TheCodeCrafter is correct. If you think you’ve detected a bug, you should use the Three.js issue tracker on github. Please complete a issue there with an accompanying jsfiddle or similar which shows the code which exposed the bug.
In your file linked on github both svg have a style=“visibility:hidden” attribute. After changing them to “visible” I could see a thick brushstroke and some thin lines.
Wow. Even I didn’t know about that. Well, then again, I never use the SVGRenderer and the CSS3DRenderer. I just don’t like using those. I don’t think I want to need them either!