Currently the server upload.wikimedia.org reports "text/plain" as mimetype for svg-files instead of "image/svg+xml". Thus Browsers cant display the files!
$ curl -I https://upload.wikimedia.org/wikipedia/commons/5/5f/Rdf_mapping.svg
HTTP/2 200
date: Sun, 05 Nov 2017 12:32:42 GMT
content-type: text/plain
Is it all SVG files? Or just that one specific one?
I saw another one shortly (but don't remember which), so I assumed it beeing a server issue – but I have now tested a handful random other svg's from commons and there it works. So seems to be about specific ones.
related to T131012 ? The file doesn't appear to have an XML prolog (although as that ticket notes, one probably shouldn't be required)