I still can't comment on this or other people's Blogger sites. Infuriating!
I'm very wary of using the word 'can't' of God. It's a sort of hyper-Arminianism I come across quite often; God can't force us into Heaven, and now there's a string of other things he can't do either. He's supposed to be an omnioptent being, though, and in that case there can't be anything he can't do!
Luke speaks of the Holy Spirit's presence repeatedly in his Gospel. Elizabeth and Zechariah are filled with it, it rests on Simeon. Then Jesus is filled with it. It doesn't seem to be the least bit inhibited before the Ascension, so I think there's something else going on. Elizabeth, Zechariah and Simeon all prophecy, paralleling passages in the OT where people are filled with the Spirit, and prophecy. Jesus is filled for the duration of his ministry, then, when it's time for the church to continue his mission, the Spirit fills the disciples. Wherever God is acting, the Spirit, which in Luke is like the active presence of God on Earth, is also present.