Kartik Prabhu replied to a post on css-tricks.com with Don’t forget the namespace for xlink. Had this issue a while back and wrote about it https://kartikprabhu.com/articles/href-in-svg
Kartik Prabhu replied to a post on commentpara.de and to a post on kartikprabhu.com with The point isn’t about XML validation. It’s that different browsers do different things when the namespace is not included.