"My personal secretary has your name."
Translation:Η προσωπική μου γραμματέας έχει το όνομά σου.
So, I got this sentence on the "Mark all correct translations" exercise, and I was marked wrong for not also choosing Η προσωπική μου γραμματέας έχει το όνομα σου...I had noticed that option and I thought it was especially included in order to make the learner aware of the correct accentuation. Is the extra accent not required on proparoxytone words when followed by a clitic? (Even if it is not, I don't really think that it is a fair exercise when the only difference between two otherwise identical choices is a single accent).
You are right. When the course was created, the rule about double accentuation was omitted. Now, the tree is locked and we cannot change the greek sentences, but we added the correct ones (double accent mark) as best translations, too. In "Mark all correct translations" exercises, duo picks the best translations as correct, which unfortunately include the aforementioned wrong sentences. This is to be corrected when we are out of beta.
"Your" is σου for singular whereas "your" for plural is σας. The plural can also be used if you want to be polite or formal situations. For example, to people you don't know, or people of some authority (p.e teachers, boss etc) it is usual to use the second person plural when talking to them directly.