@Laure @Feelew The accepted answer in that second Q&A is fairly good. The reason I changed "for" is as the answerer writes: "It would come across as overly academic, or possibly epic or religious." In fact, "for" meaning "because" wouldn't even appear in academia today, except maybe English literature — it's very poetic and would prompt laughter outside of a literary context.

(I wonder if it came up because, if I remember right, « car » is of a pretty common register in Canadian French but is loftier in Europe, and dictionary entries like WR's translate both registers, making "for" seem like a possible equivalent to the Canadian French one!)

As for "since", I've seen the complaint about its being ambiguous before, but the caution against using it in the sense of "because" on that account is more or less pedantry. It's in frequent use in middle-ish registers, being a nice middle ground between the clunky "because" and the very informal "cuz". Perhaps it should be avoided if the antecedent really could suggest a temporal relationship. I might use it similarly to « puisque » , if I was more confident in French nuance. :)

(But if one wanted to be very careful about "since", "because" would work almost equally well in Feelew's post; the register would just be a little more neutral, a little flatter. Also, "because" would insist a tiny bit more on the importance of the cause for the given effect, whereas "since" can allow a minor concession like "I don't know much about it" to slip by without signalling to the reader that it's important to recognize the causal relationship there.)

(P.S. The comments on that answer are good, and the next answer that quotes the Longman dictionary qui précise que "since ... [is used] when giving the reason why someone decides to do something or decides that something is true" may be on to something, though I'd have to think about it to see whether the generalization works.)

To close this li'l spiel here: I notice that ELU is a mix of language enthusiasts, editors, and pedants (in the worst sense of the term). Many questions have very mixed results compared to the levelheaded FSE, because in the grand tradition of pedantry, they speak with undue authority and deplore common usage and language deterioration, which is popular and garners votes. (One of my favourite sentences in a pedantic article I once saw began, "Contrary to almost ubiquitous usage..." Red alert!)

@LukeSawczak I agree with the pedantry of some of the answers... but on the whole I find it the best Q & A site about the English language. The SE system of peer evaluation and moderation make it much better than e.g. Wordreference or yahoo....

As far as levelheadedness is concerned you'll find ELL is much better than ELU. ELL is much closer to French Language since on FL we have far more non natives than natives of the language.

@Laure Merci. I might get into that one.

@Laure: « Comment ça se passe, d'ailleurs, la vie ici, dans la cité ? ». Ça me parait complètement normal comme phrase, si la cité vient de s'être glissée dans la conversation.

Je serais embêté si je devais répondre quelque chose à la question. Je ne pourrais dire que oui, selon moi, t'as tout compris et s'il y a des différences régionales, ou générationnelles je n'étais pas au courant…

À ce qui intéresse vraiment celui qui a posé la question, tu réponds « Sinon est très souvent employé à la place de par ailleurs pour introduire un changement de sujet dans la conversation. », mais c'est là qu'il faudrait une référence, ce qui n'est pas facile à trouver. Personnellement je trouve la description donnée dans la question meilleure.