On a standard display with the scale of 100%, the BoxLayout sample has blurred edges.

It is the result of how SVG is rendered: the strokes fall between the pixel grid, therefore a 1-pixel wide stroke is blurred between the previous and the following pixels with 50% of colour on each pixel. It doesn't look as good.

The above is not an issue for High DPI displays. On the display with scale of 200%, the lines remain crisp.

The images of BoxLayout-1.svg rendered in Firefox on displays with scale 100% and 200% are attached.