There are lots of replacement sights that don't require modifying the slide.
I suppose it is dependent upon the vintage of the pistol. The rear sights on my "pre-series 70" Combat Commander are integral to the gun and would require cutting.
Jim's Rules of Carry: 1. Any gun is better than no gun. 2. A gun that is reliable is better than a gun that is not. 3. A hole in the right place is better than a hole in the wrong place. 4. A bigger hole is a better hole.
no guns = might makes right