This is good. Thank you.
And you beat me to it. I wasn’t planning anything similar, but you have captured almost perfectly my own frequent observations/emotions about these sign-offs.
In fact, there was a time about ten years ago when — I’m not proud to admit this now — I would semi-seriously harangue Americans I knew who used “Cheers,” reminding them that they were not/not British and should therefore either emigrate or use one of the many suitable American turns of phrase available to them. I don’t do that anymore, but I did write these…http://enoughrope.info/category/british-invasion/ and have even more I haven’t posted, so, as you can see, it’s an ongoing theme.
I use “cordially” for letters, but confess to “best” for most emails. You are probably right that I don’t always want the best for my correspondents, but I might want the best for the subject at hand, might be declaring myself “best” in same way I would be “yours” or “your servant,” or might be urging my interlocutor to seek to be her/his best.
Or I just never thought about it until you wrote this lovely piece.
It’s the best.