The late Sol Adler was the most distinguished practitioner of the English language who ever turned his attention to "polishing" in china.
I looked up the Oxford dictionary, and it says "ever" has four meanings:
I don't think any of these meanings make sense in this sentence.
"Ever" here suggests that among those practitioners who spent some time thinking about "polishing" in China, Adler was the most distinguished - not just in this area but in the field in general.
Without it the "most" would make no sense. Without both "most" and "ever" the sentence would say simply that he was distinguished and that he thought about "polishing" in China.
What's interesting here is that a single comma would change the meaning to number 3. In my opinion, this is probably the way the sentence was intended to be read. While the accepted meaning is technically correct, it's an awkward way to word the information -- there would normally be a "has" or "had" (depending on if he was so at the time, or if he retains that status even now) between the "who" and "ever."
But with the comma: "The late Sol Adler was the most distinguished practitioner of the English language**,** who ever turned his attention to 'polishing' in China."
Consider it in this case a synonym for constantly, incessantly, or more directly, "forever." It would have absolutely nothing to do with how distinguished he was or wasn't, or whether most is used. More frequently used in the past than present, and in British English than American English, and slightly formal.
The late Sol Adler was the most distinguished practitioner of the English language, who ever [continually] turned his attention to polishing ...
"She was ever going on and on about the most trivial things. Such a bore." "Ever the gentleman, Lord Whoever greeted each guest personally."
Or a slightly different tone "My cousin is ever so boring, it's all work, work, work with him, and his job isn't even something interesting."
Of course, the ending of the sentence doesn't really make any sense using either interpretation. Is the man continually working on translating the word "polishing" while in China? Is the intent to imply his practice to say he was continually working on polishing-as-in-improving/perfecting his or other people's English language skills in China? Is it intended as a euphemism? Is the "in" supposed to be "his" or "the," making the "China" a reference to a collection of porcelain dishware rather than a nation? That's something you'd have to figure out from contextual clues.
