possessives - What's the subject? "You telling me that is galling."

Reading other questions, a sentence from this question, A single word for "hurting of one's pride", caught my eyes.

You telling me that my question asking abilities are poor is very galling.

I guess this sentence has no problem, as there's no mention about this on the page, but I cannot be sure of what the subject of this sentence is. Since, you has a form of subject pronoun and the following clause, telling me..., works as a participle clause, it seems you would be the subject. However, if you is the subject, the verb should be are.

Furthermore, the sentence's meaning is that the fact that you're telling me such thing is galling, not that you are galling. So, I think you should be possessive your.

Which one should I use here: you or your?

Answer

The subject is the noun phrase:

You telling me that my question asking abilities are poor

Where the crucial noun is the gerund telling.

Some grammar sticklers would say that for this to be correct it would have to read Your telling...