I really respect this way of dealing with unreasonable complaints. I guess the term for this is "killing them with kindness", and it's much more healthy than escalating things with a rant about how "entitled" the complainer is.
Ideally the complainer will see how positive the developer is being and reflect on their own attitude, but even if they don't, it gives a good image to other people who read the messages and sets expectations for how people should behave, so that a project doesn't devolve into toxicity.
I'm glad you took the face-value interpretation there.
Sarcasm is easy to disguise in pure text communication.
Back in the day when I spent as much time on comp.lang.perl.misc and scarydevilmonastery as I do in HN these days, that sentiment was less ambiguously delivered as "HTH, HAND, FOAD"
Ideally the complainer will see how positive the developer is being and reflect on their own attitude, but even if they don't, it gives a good image to other people who read the messages and sets expectations for how people should behave, so that a project doesn't devolve into toxicity.