I think it's actually the opposite: People who change the title every time they post are very often noobs, as can be told by the titles they choose: "That's not what I said", "Solved!", "Try Java", and similar completely worthless titles. That is why they get nag messages.
I do not
do that, and I have never
done that, and yet I definitely have received nag messages.
My impression is that you guys like the subject line to stay the same because you don't have a good way to display threading in your search results.