This question was motivated by an interesting comment that was made at https://academia.stackexchange.com/posts/comments/123681?noredirect=1
Part of Answer: I don't think that particular research team would be a healthy place
for you. The guy behaved badly. You need an advisor you can trust to
act like a mensch.Interesting Comment: Your "be a mensch" comment might be a little localised for American
English, I (as a British English / German speaker) wondered why you
were telling them to "be a human" before realising it was probably a
Yiddish import from the American Jewish community with the appropriate
semantic shift.
(I was using it in the decent human being sense; I checked the Wikipedia List of English words of Yiddish origin, and mensch does appear, in case that's helpful.)
Is "act like a mensch" too localized for ELU readers? Please say which variety of English you speak: American, British, Indian etc.
— Edited to add: I would also like to know if the context made it clear enough or if I should go back and edit the Answer over on Academia and avoid using the word in future.
(If the conclusion is yes, then I will write a separate question asking for alternatives. So, please, no alternatives here—thank you!)
Best Answer
Nearly fifty years old, born in the UK, living in N. Italy for too many years, but a frequent visitor to the UK and Ireland: can't say I have never seen ‘mensch’ online, or that my mind exploded when I read the OP's sentence. By the way, should it be written with a capital letter?
In its proper context, the meaning of ‘mensch’ was easy enough to guess. But I'm used to guessing meanings: living in Italy there are so many different dialects, you have no choice but to develop a sense of intuition. I think this is a common characteristic among speakers of more than one or two languages.
However, if knowing its precise meaning of was of real importance, it's easy enough to look it up online. I would not recommend using this term in speech in the UK, unless you were sure your audience was familiar with the expression (and this holds true for the US as well), but it might be a handy trick in a presentation which is lagging pace; a humorous side-note added by the OP: "for the gentiles in the audience, ‘mensch’ is Yiddish for a person of honour". Said with a smile and a wink, it would be memorable.
UPDATE
I have just read the cited question on SE Academia, a very interesting read, and I would like to assure the OP that it would be impossible for any reader to interpret the Yiddish ‘mensch’ in his answer as being offensive or an insult. The context makes the meaning crystal clear, so I would advise the OP to not edit his answer. Moreover, the term is listed in Dictionary.com, one of the most visited online dictionaries, which hopefully dispels any worries that it is not acknowledged or accepted as being (also) English.
2nd UPDATE (Less than one year later)
The following was written by the ex-host of Top Gear, an Englishman called Chris Evans, for an article in the Mail Online (22:43 GMT, 9 July 2016)
Which kinda proves that even Englishmen know the term and are confident enough to know how to use it correctly.
Link to The Guardian (for those who can't stomach the Daily Mail)