Nark and Little Toe,
Nark: "In your example with "the King / His Highness" the identification is only clear because the two expressions are known as equivalents in the reader's/hearer's usage." ... Littletoe: "though I appreciate that it can be translated the Lord Holy Spirit and the context seems to be predominantly filled with activity of the same."
This is the point ... and maybe I have erred in strict ancient Greek grammer, but overlaid a "known equivalent." Notwithstanding, the real use and purpose of Acts 13:2 was to show that the Holy Spirit is a person who speaks and exercises his own will. I will still look for the source reference which gave me the view that Lord and Holy Spirit were the same, because of the wording using the subordinate clause. When I do, I will post it. Doctrinally, they are the same, for the Holy Spirit is known as Lord and giver of life. However, doctrine should never dictate rules of grammer.