I've heard someone say "Much obliged!" a couple of times, instead of the usual "Thank you!". A common phrase in Portuguese ("Muito Obrigado") and maybe other languages, but certainly unusual in English. My question is: is it old-fashioned? Polite? Or pedantic?
In Britain it is a fairly normal everyday colloquialism, used in different ways. For example:
When someone has done you a favour: 'Thanks indeed, much obliged!'
A farmer speaking to someone who has asked permission to walk across his land: 'Yes, that's perfectly alright, but I'd be much obliged if you would close the gates behind you as you go'.
Reporting an experience to a friend; 'I felt very much obliged to the policeman who helped me get the car back on the road.'
Obligation means indebtedness, so to use it in the phrase "much obliged" is to say "I am indebted to you". I would say it is polite, but no more so than a prim "Thank you". It can also be considered old-fashioned; it originated some time in the late 1500s and became popular in the 1600s. It's used much less today. However, it's only slightly older than "thank you":
There is a subtle difference. "Thank you" is just a statement of gratitude. (which will quickly be forgotten)
"Much Obliged" is an acknowledgement that the recipient of the kindness or courtesy is now obligated to return the favor, or pass it along to a 3rd person when they are in a position to do so.
It's a kind of cowboy karma.
It's a hokey version of the more informal (between good friends) "thanks, I owe you one!"
I don't consider "Much obliged" to be "hokey" at all. That said, in conversation, it is a bit dated, but in correspondence, especially in email, it is similar to "Thank you" but with the feeling of indebtedness others have mentioned here.
It is indeed a more sincere way of saying "I owe you one," something that is quite casual and to me sounds a bit flippant.
Reading the above comments gave me (and surely would give non-native speakers) the feeling that it is very hokey ("cowboy karma" ?? lol) but I beg to differ!