My opinions on this are that the question is inherently opinion-based, and in this specific case, also too broad to be able to be effectively answered, and that it is a recommendation request.

First, the question will result in opinion-based answers because it centers around a medium that is without an empirical standard of quality. We can talk about bitrates and the power of the DAC that processed it, but it still comes down to how it sounds in our ears. Granted, this is the weakest of my arguments.

Second, the question is too broad because, while it does state it is about a specific circumstance, that of storing 16-bit PCM audio for archival purposes, it lacks information on how it will be archived, the equipment is must remain compatible with. It appears to assume that encoding/compressing the audio file itself is the preferred means, and fails to account for file-compression options which are better suited for archival purposes, especially is the optimum solution will be that the file can be retrieved from the archive at the best quality level it was archive at, which would, by definition, be the same file.

Third, the question is seeking recommendations for a tool to accomplish a task. It is not asking how to compress a given audio file for archive, it is asking us to suggest a preferred form for that archive. The fact that "highest compression* is stipulated rather than the more obviously opinionated best is a quibble and not a real differentiator.

The question could be modified to "How do I archive audio files with the intent of retrieving them later at native quality" and it would be OK. Right now it is "What is the best way to archive audio files for best quality", and that is off topic.

My opinions on this are that the question is inherently opinion-based, and in this specific case, also too broad to be able to be effectively answered, and that it is a recommendation request.

First, the question will result in opinion-based answers because it centers around a medium that is without an empirical standard of quality. We can talk about bitrates and the power of the DAC that processed it, but it still comes down to how it sounds in our ears. Granted, this is the weakest of my arguments.

Second, the question is too broad because, while it does state it is about a specific circumstance, that of storing 16-bit PCM audio for archival purposes, it lacks information on how it will be archived, the equipment is must remain compatible with. It appears to assume that encoding/compressing the audio file itself is the preferred means, and fails to account for file-compression options which are better suited for archival purposes, especially is the optimum solution will be that the file can be retrieved from the archive at the best quality level it was archive at, which would, by definition, be the same file.

Third, the question is seeking recommendations for a tool to accomplish a task. It is not asking how to compress a given audio file for archive, it is asking us to suggest a preferred form for that archive. The fact that "highest compression* is stipulated rather than the more obviously opinionated best is a quibble and not a real differentiator.

The question could be modified to "How do I archive audio files with the intent of retrieving them later at native quality" and it would be OK. Right now it is "What is the best way to archive audio files for best quality", and that is off topic.

UPDATE: Responses to comments

1. This is the First time I have made this argument on this thread. I used this argument previously in a comment on the post that is the subject of this discussion. But, as is the norm in SuperUser, I do not expect people to go there and read my argument there to get my first point. Instead I include ALL of my arguments here for simplicity and clarity.
2. Arguments remain arguments regardless of being false or not. They may be invalid or invalidated, but they remain arguments.
3. Audio quality has quite a lot to do with it, primarily because you specified "lossless" as the preferred compression/encoding type.
4. When encoding audio using a different codec than before, you MUST give consideration to the desired playback. If you encode the file using a codec that is not supported on a potential future system, that file is useless. Changing the codec is serious business, and due care must be taken when doing so.
5. Don't assume.
6. I suggested how the question could be rephrased in a way I thought would get rid of the opinion-based or recommendation-request aspects of it. This alone indicates that I see there is merit to your question and that there is something to it which can and should be answered here on SU. I attempted to help you suss that bit out.

To summarize: This is a community. Out of respect for you I gave a brief synopsis of the reason why I voted to close your question in my comment on your question. When you came here, I gave a fuller explanation. You are also free to accept or reject my reasons. I'm not saying my idea is best or should win. Clearly others disagree with me which is why your question now stands open again. But what this community also is is respect. I didn't have to provide any reason, but I respected you and the community enough to do so.

Make of that what you will.