Real, reliable production of the comic ramped up in 2006. This comic ran at the end of 2010, so by this point I’d had three years of replying to multiple helpful readers pointing out that I had put the wrong copyright date on the comic. They really did! Multiple people! Every year, every comic that had the earlier copyright date. Some of them got surprisingly snotty about it.
The sheer repetition of the issue is what caused my tone to turn so combative.
If I ever am in a position to publicly berate someone, I hope I have the wherewithal to do it while wearing a smoking jacket and an ascot.