My good buddy who has been Evangelical for a long time now says that he is the best interpreter of what Scripture says. Period! Maybe that is why it is called Sola.
Did he turn into the person of the Trinity?
Well then your good buddy is following scripture:
Philippians 2:12 (KJV)
Therefore, my beloved, as ye have always obeyed, not only in my presence, but now much more in my absence, work out your own salvation with fear and trembling.
Remember that on judgement day, each individual will answer for their own sins and what they have done for salvation. Neither the Pope, priest, parent, nor partner will be able to answer for the individual. Only the individual themselves. Therefore, because it is their soul/salvation that is on the line, they are the best judge as they are the one who will pay the price for any errors in interpretation.