My Dad's 4 1/2 has the corner chipped off the lever cap - I think he was taught to do that at school, too!
I haven't replaced it - it causes no issues in use. IMHO, it's more important to ensure the chipbreaker contacts evenly across the iron, as that acts to distribute the pressure from the lever cap.
I don't use thick irons, just ones that are close to the usual 'double irons' for Stanley and Record. I found I got a noticable improvement when I flattened the chipbreakers where they contact the iron, so that there was a single straight line across. Several I had were distorted in manufacture so it was a curve across - only touching the iron at two points. IIRC the lever cap actually presses flat down on the top of the 'hump' in the chipbreaker, and on a couple of the Stanley ones I have, that's slightly behind the extreme end of the lever cap.
If you want to see what's actually happening, use a whiteboard marker to 'blue' the back of the chipbreaker (where the lever cap touches it), then fit it and gently remove it again and see where the colour has rubbed off. Same with the business end of the chipbreaker. You may find there's nothing to worry about at all.