If I was their partner I would read this as, "Oh, they understand that we have two different ways of communication and they are changing their own behavior instead of asking me to change mine so that we both end up saving time/money. This is what it looks like to be a good partner? Pointing out that your partner thinks differently from you is not the same thing as blaming them for something.
Could you explain, in your own words instead of putting the responsibility on me to interpret your meaning, how they are blaming their partner for the interaction?
Indifferent, probably. The thing missing from the post is the conversation where the miscommunication was identified and discussed, so I don't know how his partner would feel. In this hypothetical, I'm the partner, and I'm the kind of person who knows all relationships have communication errors. If we recovered gracefully, then saying "20 minutes late and $20 down" is hardly dirty laundry. Would probably even appreciate that he uses it as a reminder of how to reduce ambiguity communicating with me, as I have my own reminders of how to reduce ambiguity communicating with him.
No. Do not imagine it nor ponder it. Go right to her and ask.
And in the long run, she needs to be coached to articulate without being asked every time (if that is the case with her).
Generally, when people start imagining how I feel about X, they are wrong over 50% of the time, which leads to an escalation of problems. Don't wonder how I feel. Ask me explicitly.
As for the wider discussion: The path to Hell is paved with good intentions. I struggled with this often until I read some negotiations books, all of which said "Don't give credit to someone who did something for you that was of no value to you, and signal to them that this is of no value so that they do not expect a concession from you as a result." For random one offs with random people, it's fine to appreciate their (totally wasteful) effort because you don't have to deal with it often. But in a long term relationship it becomes a currency and causes long term stress. Not only are these efforts creating problem for you (money wasted, time wasted, etc), in the long run the other party will expect credit for it, which will feel like an added insult to injury.
