How can there be so many linear gradients? I am working on a document that uses only one swatch, but there are still loads of linear gradients that are just black. Even after I go through the SVG document with a text editor and change the fill or stroke of each element to the same linear gradient, save the file, open it in Inkscape, and vacuum defs, there are still lots of them left over. I finally removed all of the extras with the text editor. BTW I am using JessyInk. Where do they come from and how do I avoid all of the duplicates?

Hi.

There is a known bug, of storing every gradient with small editing of the gradient steps.
Most of the time it happens when you clone an object, and edit the gradient steps on the parent object, with the node tool.
The vacuum defs should solve that, so I'm not sure what happened with your file.