As you've probably guessed, the person on the other side of this email thread was taking action that I wasn't happy about. At least in my mind, when you say 'thanks for understanding', you mean something along the lines of 'I know that what I'm doing/saying/planning on doing might not be what you think I should do, and I'm glad you realize why I have to do this'.
But now that I'm reading that, I realize that's a pretty complicated meaning for a little three-word phrase, and perhaps I'm the one that's out of sync with everyone else. So I decided to check this phrase out on the internet. I found a site called Englishtown, an online school for developing English skills. Ok, that sounds like a pretty reliable source. Englishtown recommends using the phrase "Thank you for your understanding" in a letter if you've shared something that may inconvenience or negatively impact the reader. As it happens, that's not far from the actual situation here. So maybe it's just me.
But wait, there's more. I found a blog post in which the author complained that they didn't like it when someone expressed thanks for something that you hadn't done yet, in the hopes of persuading you to do it. Well that doesn't fit, because it's not as if there's anything the other person wants me to do. Except that this post went on to say that one of the reasons the author didn't like the 'thank you for understanding' phrase was because she didn't want to be understanding, she wanted to be selfish and have things her own way. Now before you rush to judgement, this isn't a situation where I wanted things my own way... and frankly, it was someone else being inconvenienced, not me. And if you ask me (I know, you didn't ask... but IF you did), the person who was saying thanks was the one who was being selfish.
And that's about all I could find about this little phrase, with the exception of an amusing little anecdote. Someone told a story of being in a foreign country. When they entered the inn they would be staying at, no one was at the front counter. But there was a bell on the counter next to a sign that said "Thank you for your comprehension." The individual did comprehend the situation, and she rang the bell. Sure enough, after she rang the bell, someone came out to greet her. Here in the US, we would have said 'thank you for your understanding', but 'comprehension' was as good a word as 'understanding'. So perhaps in my situation the sender of the email should have said 'thank you for your comprehension of what I've told you I'm going to do'.
And that's when I realized what the problem was. You see, there are all sorts of forums where people inquire whether it should be 'thanks for understanding', or 'thanks for your understanding', or 'thank you for understanding'... and they're all missing the point. The person who sent me the email actually intended to say "thank you for being understanding"... using the definition of understanding as being tolerant and forgiving.
They're still wrong... I'm only tolerating their actions because I have no choice, and I don't really forgive them... but at least now I know what they meant, and why they felt that had to say it twice (see the persuading notion, up above). Had they known me better, they might have chosen to say something like... 'this is what I'm doing, so go have a cup of tea'. No, tea doesn't change what they've done... but it does make me feel better.
My response to all of this?
And after it's all over... go have a cup of tea.