I've been thinking about a curious issue in translation, which is not that uncommon. In most ordinary contexts, the Polish "ręka" and the English "hand" would be interchangeable in the sense that where a speaker of one language would use the one, the speaker of the other would use the other. Where the English-speaker talks of having something in his hand, the Polish-speaker talks of having it in his ręka, and so on. But the two terms are not synonymous. In non-medical Polish, "ręka" refers to the whole of the upper limb (though in medical Polish, it refers just to the hand), while the English "hand" refers only to the area from the wrist to the fingertips. The Polish term referring to the exact same part of the body as the English "hand" does is "dłoń", but the word is significantly less used than "ręka" (as per Google hits in .pl sites, say), and in many ordinary contexts using "dłoń" for "hand" would make for awkward translation. Conversely, to translate the Polish "ręka" as "arm", which would refer to the same part of the body (I am assuming that the arm includes the hand), would in most cases lead to awkwardness as well. It sounds funny to talk of picking up one's phone with one's arm, and so on.
Thus, it seems that these are cases where the natural translation from one language to the other does not in fact preserve the truth conditions. One can pick up one's phone with one's ręka without picking it up with one's hand (say, use the crook of the elbow), even though in the context of picking up a phone one would translate "ręka" as "hand", unless it was obvious from the context that the hand wasn't the part of the arm that was being used.
Maybe what is happening here is that when a sentence asserts a proposition p and implicates a stronger proposition q, we feel no qualms about using a translation that asserts q, or vice versa. To say in Polish that one picked up one's phone with one's ręka implicates the stronger proposition that one did this with one's hand, since if one had picked it up in the unusual way with the crook of the elbow, say, we would have expected the speaker to mention this. (This is a case where the usual Gricean presumption that one will use an equally brief but more precise term in place of a less precise one is defeated by the fact that the more precise and equally brief term "dłoń" is also less commonly used.) So one translates the implicature rather than the assertion.
I wonder, though. Maybe cases like this are evidence that the distinction between implicature and assertion is artificial. This would have the important consequence that the wrongness of implicating contrary to one's mind, or at least intentionally doing so, is the same sort of thing as lying. I don't want to embrace that consequence in general. I think false implicature is qualitatively less morally problematic than lying.