Comment 3 for bug 1550902

Also confirmed on Xubuntu 15.10, Inkscape trunk rev. 14695.

But opening the defs element in the XML editor shows that each marker is different. They all share the same stockid (reference to the original marker) but all have a different id. I guess it's not a bug, but a feature to allow you to customize each marker (with a different color or a different transfom attribute).
That said, it would be useful to add an option to use a clone of the original marker, with the possibility to unlink it when a change is needed.