This forum used to do that, too (put the name of the person you were replying to in your reply post). But when we upgraded to a newer version, they eliminated that feature, for some strange reason.
So now most people use a quote in their reply to let you know what they are replying to.
I think most people read the forum in flat mode, despite the occasional confusion when people switch subjects within the thead.
I don't know why people change the subject line within a thread. If you are changing the subject, why not start a new thread?
It is just too easy to get off on tangents, because one thing makes you think of another thing, and on and on until we are talking about space shuttles to Mars.