I just got home from grocery store this evening and had a run-in with another costumer behind me in check-out tonight which went like this.
As I was paying, the lady behind was kind of ditsy with her change getting into the conveyer belt and was annoyingly staying that she might ruin it. I looked at her and said "Oops" Then she scowled at me.
A few minutes later, I was trying to pay the cashier and asked her three times for a pen. By the third time I asked her in a firm manner without any emotion" which is when the other customer asked me the question above."
I just ignored her but she did make me feel uncomfortable because those kinds of comments are a hot button for me.
I responded to her with an off-putting comeback that I learned from another aspie who mentors others on how to handle people who make similar comments which is, "Purple tuna fish," which shut her up.