Some text in some SVG file seems overwritten in Mousepad. I was trying to replace one color in one file but was too difficult. Here is a screenshot http://i.imgur.com/41wc2WN.png Here is the link to a file: https://upload.wikimedia.org/wikipedia/commons/e/ec/Arctic_big.svg I've tested it on Leafpad and it had the issue also.
Saving the SVG file via Firefox does something strange to the formatting. No problem when using wget to fetch it. I assume that the buggy handling of long lines needs to be fixed in GtkSourceView, so I suggest to forward this issue to the GTK devs: https://gitlab.gnome.org/GNOME/gtksourceview/issues
I tried to open the faulty file with gedit, but it just froze without displaying a window. Similar bug report for Pluma: https://github.com/mate-desktop/pluma/issues/197
https://gitlab.gnome.org/GNOME/gtksourceview/-/issues/121