I am a native Canadian English speaker. I've heard people say, "Thanks a lot! Thanks a million! " "Thank you very much" seems to be the most commonest. Some people say "Thanks so much". "Many thanks" sounds okay to me.
"Sincere thanks" or "Many thanks" sounds okay too.
Oh yeah, sometimes I've heard people saying, "Mercy buckets" when they were trying to be funny and they meant "merci beaucoup".
Sometimes "Thanks a lot" is said sarcastically, kind of like a joke. For example, if the person says or does something that the other person doesn't really appreciate at all. They actually mean the opposite of "thanks a lot".
You make a good point. It is so true that so much human communication is delivered with not only words, as you say. Tone of voice, sarcasm, an angry face, etc. I don't know the answer, but I do know that when my child says "Thanks a lot, Mommy dearest!", turns her back and slams her bedroom door shut, she is neither grateful nor does she find me endearing in any way, (ideally temporarily).
"Thank you really" is awkward syntax in English, but it is the preferred translation? I had, "Thank you sincerely" (sounds a little better) but it was marked wrong. As we all know "sincere" is from the Latin, literally "without wax", and it refers to flawed marble slabs and blocks where dishonest vendors would hide the defects with melted wax. You would always want a piece of marble "without wax" or to be "sincere"!
lol. we do that in modern times with apples - they are coated in wax to make them look shiny and delicious, and to disguise the fact that they have been in cold storage for a year but actually taste like crap! maybe we should ask our supermarkets for sincere apples . . . . . seriously though, what interests me about this exercise is whether << merci, vraiment >> actually gets used in French and what the intention is so I can understand the underlying meaning and how/when to use it or understand it if I hear it.
As an English native I agree 'really' is a very popular word to emphasise an adjective. ' Wow this is really good! is an example. But to emphasise thanks? Hmm I am not so sure. 'Many thanks might be used in writing at the end of a letter or email as might be 'thank you truly' or 'thank you sincerely' but no so much in speech as it rounds a little insincere. Personally I would stick to Thank you very much or merci beaucoup any thing else in either language sounds like irony to me.