Yea your right, those are hilarious!! I admit i have clicked on a "related" thread at the bottom before and got into it and then responded to it myself, sometimes catching it and editing or re replying to my own post saying that i remembered that i clicked a related Old thread, sometimes not catching it till someone else points it out.
It is funny though when someone metions something for sale etc or a problem and someone must be searching thier tractor or something and then offers to buy it o help them fix it, i guess not realizing that the thread is like you said 4 years old!