This is the 19th post in this thread. :shock:
I have to say that, in my opinion, most native speakers would not notice whether someone said 'your' or 'their' , or 'name' or 'names'.
Yes, I agree with you and know that most of you native speakers do not and do not need to care so much about whether someone said "your" or "their", or "name" or "names", for whichever is used in this situation, the job will be done and in real life there will be no controversy among those involved although semantically there is ambiguity in some versions of the sentence. Anyway, language is not logic and ambiguity happens very often in real life language use but our human reasoning power will always help us figure out the speaker's real intention.
Then why do I care so much about this language issue? The reason is that over here I am in a rather different English language learning environment. Some so-called English language experts here in China would often say a certain expression or structure is the only correct expression or structure for an idea when actually there are alternatives, which they do not know at all. And I have also found that it also often happens that some expression or structure they say is wrong actually is 100 % correct and is used by (some/all of) you native speakers; the language issue right under discussion is a good example. It is my determination not to follow in those Chinese "English language experts"' footsteps; if possible, I always want to know as much about a certain English language issue as possible and then explain it thoroughly to my students in or after class. It is for this very reason that I am seeking help from you guys with this language issue. Therefore, you may now have realized that I am not making a big fuss about something trivial if you take my perspective at this asking; this language issue is of great importance to me and my students, and I want to teach myself and my students how to learn English in a more effectively and better way.
My thanks go to you and all the others who have replied to my questions.