singular they

[sereshka]

   В каких случаях вы считаете оправданным употребление they в значении единственного числа, когда пол человека неизвестен? 

1. Everyone should drive their cars on the right side of the road.
2. A student is expected to turn in their homework.
3. A friend lent me their keys.
4. A LiveJournal friend sent me their condolences. 
5. Dr. Zhu has presented their results at a conference.
6. A paper reported on the discovery made by Frule Mozgol. Their findings are shocking. 
7. Anyone can scratch their noses.
8. When asked about the situation, the politician, who wished to remain anonymous, stated their party position rather than their personal opinion.
9. Hospital records revealed that the kidney was donated by a person named Prikle Tuffinen. Their contribution is sincerely appreciated.
10. Hospital records identified the donor as X. Their contribution is sincerely appreciated.
11. Hospital records indicated that the kidney was donated by an anonymous donor. Their contribution is sincerely appreciated.
12. A lawyer is expected to listen to their client.
13. The paper ran an editorial on the findings of Frule Mozgol. Their journalistic ethics was questionable. 

Comments

[sereshka.livejournal.com]

So, 8 works, in your opinion?
What if in 3 you know the gender but don't want to give it out? (I personally find this sentence very awkward, but at least one grammar manual says that it may be acceptable, if you don't want to identify your friend.)

[ikadell.livejournal.com]

Well, yes, 8 sounds stupid, but it works.
If you don't want to give out, I think it's better to structure it differently: I borrowed the keys from a friend (for instance).

I have seen people use ze. It looks even worse.