He is right because of one simple thing: there's no guarantee that I would see this. I only saw it just now because I was bored and I wanted to see if there were new posts in the following forums:
General FreeSpace Discussion
FreeSpace & FreeSpace Open Support
So I mean, if I hadn't looked until like say a week from now, then you could end up wondering why I'm ignoring you. So, threads that are directed toward just one person are a bad idea simply because there's no way to guarantee that the person would see that thread without telling them about it in a Private Message. So, you can see that it would be best to just use the PM for the entire message anyway.
It's all good though: I replied via PM.