Asteroid-Man said:
In all seriousness - so Qui-Gon in that episode... was he a force ghost or was he also one of the son's personifications?
It isn't made clear in the episode. Although I'm sure it's not one of the son's personifications, since he tell the truth to Obi-Wan about that place.
Since this arc is made of three episodes (and Qui-Gon will be back on the third one), there is more that needs to be explained.