I don’t usually disagree with you PR, but on this point I think I do. I think the HS is the interpreter of Scripture, and that He does lead into all truth.
I think that there are other assumptions that must be made in concert with this one, though. One of those is that the HS will not lead an individual or a group in an opposite direction than He has already led the Church. This foundational principle is often left out by our separated brethren.
The other is that the HS works through the leadership appointed by Christ. It is true that sometimes individuals will get the message quicker than those invested with authority, but those saintly persons always pray that the HS will give the same message to those who are empowered to act upon it.
If these foundational principles are followed (following the Sacred Tradition and the Magesterium), then the individual has great latitude in following the guidance of the HS as one is interpreting for themselves.
The reason we see problems with people being led in so many divergent areas is that they believe that it is the HS speaking when it is not. There are many voices, the world, the flesh, the devil, in addition to the HS. Most devout bible reders in all sincerity believe they are led by the HS, for example the poster above who believes that Mary was not a perpetual virgin. People depart from the teachings of the Apostles because they are separated from the other two legs of the stool.