I don't think anyone said deleting the thread was deliberate? She was trying to delete her own post and accidentally deleted the whole thread. But I don't think mods ought to be deleting their own posts without a reason (ie, a moderator reason, not just because they want to start their post...
I can't recall anyone accidentally deleting a whole thread before, though. It'd be a bit different if the forum had corrupted or something - but this is a case of someone deliberately hitting a delete key (however unintentionally), and it's not exactly a common occurrence. I hope the mods will...