I have not come across many situations where I need to use this, but it can be helpful to know and will point out what actions or inactions will make the mods lock your thread, added advantage if it just slots right in without distorting anything else.
Topic authors of topics locked by admins or moderators know the reasons, without the SMF patch, because they can not unlock these threads. If they try to unlock, they will see a following message.
Without trying to unlock the thread, a user should be almost 90% sure they were not the ones who inadvertently locked their own thread.