October 2015 (UTC) 

 :::: Some naval prefixes (like your examples) would be considered part of the common name of the ships (per "Ship prefixes should only be used in article titles if multiple reliable, published sources consider the prefix to be a part of that specific ship's common name", in all forms of the proposed guideline so far), as they would be what a non-expert reader would expect the article title to be at. As examples, this news article names the two warships mentioned as "HMAS Newcastle" and "HMAS Melbourne", the various memorials at Pearl Harbor are the "USS Arizona Memorial", "USS Oklahoma Memorial", and "USS Utah Memorial". Conversely, this article mentions over a dozen cruise ships, with not a prefix in sight, with the same lack of prefixes on this container ship company or this cruise ship company website, leading me to conclude (at least for this very small, modern-biased sample) that prefixes are not part of the common name for these types of ships. Not all navies use prefixes anyway (unless we want to start making them up, like a minority of sources do and both the existing and proposed guidelines advise against), so even if we forced prefixing on civilian ships, there would still be a number of ships 'inconsistently' un-prefixed.   09:47, 22