Hm. It's hard to say. Glancing through that chapter, I think he's reasonable for sixteen, but yeah, he could easily also be as old as nineteen.  I know a lot of teenagers, at the moment, and at sixteen, there's a lot of variation in a whole bunch of ways. Somewhere between fourteen and seventeen seems to be where kids start getting introspective, and thinking a lot about both appearances and ethics, and discussing some pretty deep concepts with each other. Once that starts, it continues for a few years. At least, that's how I remember high school, and my daughter's friends seem to be similar. It's the time you worry about what it all means, and where you fit, and if you want to.

Going back to when I was writing this, I expected Harry to have that jump in maturity of thought -- although possibly more problems in behavior -- after losing Sirius.

In any case, I'm glad you're enjoying it!