SO, ru.SO, ja.SO are svigified:
But not pt.SO:
It seems to use semi-old design (can be seen by looking at the logo).
That's also strange because pt.SO is older than ja.SO or ru.SO, but still not svgified.
P.S I don't know to which word I should append "s", so I've written Stacks Overflows, just in case.