I think the consensus/recommendation was to clear coat the decals but to be careful about doing it. Clear coat only the decaled area.

Is the paint on the frame glossy or matte? I ask because it is possible to match the surface finish on the paint by judicious polishing of the clear coated area. You spray the glossy clear coat then, depending upon the finish you want, you polish with relatively rough or relatively fine grit. The rough stuff (600 grit) leaves a matte finish. Finer grits will result in a more polished look. If you want a truly glossy finish, don't polish it at all.

Clear coat helps but will not stop a bike lock from damaging the pain or decals.