You don't mention issues and your advantages are only marginal for specific use cases such as Asian languages. "UTF-16 is better": but 'only' for Asian languag

You don't mention issues and your advantages are only marginal for specific use cases such as Asian languages. "UTF-16 is better": but 'only' for Asian languages; most code is still written in ASCII "need to commit to 16-bit char width": the OP's point was that many many tools don't operate on 16-bit char width and with UTF-8 you can continue to use them. The other two points are no advantages for UTF-16.