I did finally think of a scenario this construction could work for... i'm thinking of a top view to a immersive game, where i know the intent of the character is to "go somewhere" from a city that has a district with a port .....and a district with a highway to inland...and as game master i need to set her direction .....and in making that decision it might be important to know "which side of the city she is *going from" to get proper supplies. This is a big reach, i know, haha. I think english speakers hear the "geliyor" version (coming from) more often.
"Side" suggested borders or barriers to me; so I invented a scenario like this: A balloonist who lives near a border between two countries is about to set off on a trip; the journalists want to know where to go, to film the embarkation.... so they ask, "Which side [of the border] is he going from?" Also quite a big reach....:)
This sentence is a little odd (at least in English), but he can go from a side if the location that he's leaving has sides. I'd probably say ‘leaving’ instead of ‘going’, but if he's here, and leaving here for elsewhere through one of the sides that we have here, then I'd definitely prefer ‘going’ to ‘coming’.
Replacing it woud be a good idea, I think. I had the sentence in a listening exercise and insisted on hearing "tarafta" instead of "taraftan" because I was thinking of "going to". I'm not a native speaker of English, but "which side is he going from" sounds strange to me. Is it an idiomatic expression?
It is better in grammatical terms, and is "higher class" English, but it is not as colloquial. As a native speaker, I have no problem with "Which side is he going from?" This is what real speakers say in the street. You commonly hear people ask, "Which airport are you flying from?" "Which side of Main Street do you live on?" etc., ending sentences with prepositions with no trouble at all. This is the living language in use.