It doesn't make sense at all.
I think some people make mistakes when the post things ... and thankfully they can change them.
Gmail has a feature where you can UnSEND an entire email.
Xenforo locks your title in Forever ... even if you want to change it 10 seconds later.
It's very End User unfriendly (very unXenforo like !)
This is extra unfair to end users as they have come to expect the ability to edit titles from using other software.