I doubt it is a limitation of GTK+: Dia for example, compiled with the same version of GTK+ (2.24.4) as Inkscape, does display indicator icons of the current state in the 'View' menu for the various options which can be toggled on/off with a single menu item (unlike the menu entries in Inkscape's 'View > Show/Hide' sub.menu which use checkboxes)).
> Is it Gtk+ theme specific? ¨
I doubt it is a limitation of GTK+: Dia for example, compiled with the same version of GTK+ (2.24.4) as Inkscape, does display indicator icons of the current state in the 'View' menu for the various options which can be toggled on/off with a single menu item (unlike the menu entries in Inkscape's 'View > Show/Hide' sub.menu which use checkboxes)).