Is the Comforter a person?
The answer is Yes. The Comforter is the Holy Spirit the Third Person in the Most Holy Trinity. But a good follow-up question is, is He or She a person like Jesus who was incarnated to lived in a full human nature?
The Holy Spirit will take on the role Jesus would leave behind and that is of being an Advocate or a Consoler, Comforter and a Paraclete. The simple question is, would the coming of the Holy Spirit needed a "flesh" too like the coming of the Logos also a Spirit the Second Person in the Most Holy Trinity was incarnated?
The answer is No, the Holy Spirit will not be incarnated like the Logos but instead of incarnated the Holy Spirit would simply dwell or indwelt all the redeemed. As scriptures said the body is the temple of the Holy Spirit.
Do you not know that your body is a temple of the Holy Spirit who is in you, whom you have received from God? You are not your own; (1Corinthian6:19)
Let's take one by one your raised confusions;
When he comes, he will prove the world to be in the wrong about sin and righteousness and judgment: about sin, because people do not believe in me; about righteousness, because I am going to the Father, where you can see me no longer; and about judgment, because the prince of this world now stands condemned. John 16:8-11
You raised two good question and a good reference pointing it to a person like human;
1.It seems to me that it has not happened already that those 3 fact were fulfilled, in particula the last one, I can't say Satan has been defeated again since Jesus death.
2.How can we say that a spirit hears? Additionally the greek word is ἀκούω, https://studybible.info/strongs/G191 shows the common usage on persons.
- Jesus dying on the Cross won for us the victory over satan, and indeed Jesus condemned satan as He came to destroy the works of the devils. (1John3:8)
The one who does what is sinful is of the devil, because the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the devil’s work.
- The Holy Spirit will not only testify on the Truth about Jesus like what the Apostles did in their mission to spread the gospel, but part of it is to convict the man of their sins and wicked living because the Holy Spirit dwells in the heart of the Apostles.
And I will ask the Father, and he will give you another advocate to help you and be with you forever, the Spirit of truth. The world cannot accept him, because it neither sees him nor knows him. But you know him, for he lives with you and will be in you. John 14:16-17
This can only be the spirit because of the last sentence, and because otherwise how can he be forever?
- This passages is where the confusions mostly arises, is the "another Advocate" a real person or a person in the form of Spirit?
The passage said the "another Advocate" or the "spirit" already lives in all the Apostles although it has not yet come fully in them as the Holy Spirit will come during the Pentecost at the Upper Room to fully anoint them in their mission to evangelize and baptize the whole world.
The important question is, we go back to the analogy with Jesus Christ. We can see that the Logos like the Holy Spirit is a "spirit" and had no human flesh. Jesus became the Advocate when the Holy Spirit dwells in Him in the Baptism in the Jordan River.
16 As soon as Jesus was baptized, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. 17 And a voice from heaven said, “This is my Son, whom I love; with him I am well pleased.”
This passage shows that Jesus in the human flesh became the Advocate when the Holy Spirit came down to fully and perfectly dwells in Him because Jesus although fully man is co-substantial with the Abba Father the First Person in the Most Holy Trinity.
Now, if we ponder the scene in the Upper Room, among all the people present in the Upper Room, to whom do you think the Holy Spirit will dwell fully & perfectly to become the "another Advocate". Remember Jesus became the Advocate because the Holy Spirit was able to dwell in Him fully and perfectly.
Now, if we choose among the people present in the Upper Room. most likely who would the Holy Spirit choose for Her (Ruach the Holy Spirit in Hebrew is feminine) to fully and perfectly dwell so that She can fulfill Her role as the "another Advocate"?
It's up for us to choose among the Twelve Apostles, would it be Peter or John the beloved or would it be James the Greater as this three were all seen Jesus in His Transfiguration in Mount Tabor.
Would it be Peter that the Holy Spirit had chosen because Jesus gave him the Keys to His Kingdom in Matthew16:19 and promised His powerful protection that his faith will not fail, and also Jesus had given Peter the task of "Advocating" for his confused and fallen brethren in Luke22:32
But I have prayed for thee, that thy faith fail not: and thou, being once converted, confirm thy brethren.(Douay-Rheims)
..but I have prayed for you, that your faith may not fail; and you, when once you have turned again, strengthen your brothers."(New American Standard Bible)
Plus, the strongest passages where it seen that the Holy Spirit perfectly dwell in Peter is in Acts5:3-ff wherein it showed a lie spoken to Peter is a direct blasphemy against the Holy Spirit who dwells in him.
Then Peter said, “Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit and have kept for yourself some of the money you received for the land? (Acts5:3)
In this passage, we can see that Ananias does not know that when he lied to Peter, he is actually lying to the Holy Spirit who perfectly dwells in Peter as Jesus anointed Him and appoint him to Shepherd His flock.
The interesting part here is before Peter can "advocate" to the rest of the Apostles, Peter had fallen first, he betrayed Jesus Christ thrice..So, how did Peter rise up?
Peter was consoled and comforted by another person and She is the Theotokos. Peter now learned how to be consoled from the Maternal Hands of Mary. Since Peter learnt the art of consoling from the Theotokos. Were now left with two choices;
Who would the Holy Spirit choose to dwell to perform Her role as the "another Advocate"?
Would it be Peter whom Jesus gave the Keys and the responsibilities to console his brethren or the Holy Spirit will choose the Theotokos anyway She already "overshadowed" Her..
The answer needs more pondering....but St.Alphonsus Liguori a Doctor of the Church and one of the Great Marian Saints had already meditated the answer...