The advantage of thread locking (albeit arbitrarily) is that the inputs are not lost, and the thread can be re-opened if needs be.
Compare that with the sad deletion of threads where the thread starter in a fit of pique decides to delete his/her first post (and thereby deletes the whole thread) just because not everyone agrees with them.
Recent example the ICAO code thread, near-misses (thread-prox
) Lydd Diversion.