Mousepad should set the "highlight-current-line" property to true so that the current line of code is highlighted. This doesn't even really require a preference - if users don't like it they can disable it in their gtksourceview theme.
Created attachment 5232 patch adding option to highlight current line of code Here is a patch, adding it as an option in the view menu.
Created attachment 5233 patch with comment fixed sorry - missed updating a comment in copied code
I added most of the rest of the GtkSourceView/Buffer properties as options in the new preferences dialog/settings stuff in master. Closing as fixed.