I was just thinking why there is the “Title” text field if nobody uses it. Is it really useless by design or are we just lazy?
To give titles to messages is essential for quick reading. Some people do not even read e-mail if it does not have a subject. One of my teachers explained it like - subject should extract the most important idea from the whole message. So if a mail has its subject field empty, it actually describes all its contents precisely, right?
It is sometimes hard to decide what the subject actually is. But that is kind of a feedback, too - for example, if you are going to write about two different topics, double posting may be even appropriate.
I do not know of any web forum where people would really use this feature called titles. But I am quite sure it could improve the readability of lengthy threads - 2.5 Development Updates is the first candidate.