I used a non-mutilated version of the pizza card for a month or two (and surprisingly continued to get nice reactions from folks – just for having a pizza on the card) but I got tired of having the card without any physical damage so I created a new one.
After doing a few tests on the old card with drills etc, the best method was to melt the holes in was to press quickly with a fire-heated nail. The card has really satisfying crater-like impressions in the back of the card which you can feel when you handle it.
So far reactions from my friends have been nice - but no stranger has commented. This is a huge difference from the pizza card where almost everybody comments. My guess now is that they notice, but because of the implication of guns they are afraid to say anything. Also note that I mis-positioned one of the holes to be over the magnetic strip and had to just scratch it on the surface instead of punching it all the way through.
As always, appreciate feedback in the comments!