Burns has passed kind of into folk status, and is a special case.

What matters, obviously, is not whether Burns has passed into folk status, but whether the particular translation has. The latter seems an implausible claim (since printed translations can presumably be traced and attributed), but if it were true, then there would be no need for acknowledgement (almost by definition of "folk status").

My comment arose from the suspicion that you reacted as if Burns had been paraphrased, as opposed to translated -- because the original language looks similar enough to English that a translation will tend to look like a paraphrase. I find it unlikely that you would actually have made this comment if lukeprog had quoted Catallus without mentioning the translator; and on the other hand I suspect you would have commented if he had taken the liberty of paraphrasing (or "translating") a passage from Shakespeare into contemporary English without acknowledging he had done so. My point being that the case of Burns should be treated like the former scenario, rather than the latter, whereas I suspect you intuitively perceived the opposite.

All translation is paraphrase, of course -- but there is a difference of connotation that corresponds to a difference in etiquette. When one is dealing with an author writing in the same language as oneself, there is a certain obligation to the original words that does not (cannot) exist in the case of an author writing in a different language. So basically, I saw your comment as not-acknowledging that Burns was writing in a different language.

I would never quote Catullus or Baudelaire in English as if it were the original author's words. No. It's wrong (deprives the translator of rightful credit) -- and, FWIW, it's also low-status.

I don't see it as lowering the status of the quoter; the status dynamic that I perceive is that it grants very high status to the original author, status so high that we're willing to overlook the original author's handicap of speaking a different language. In effect, it grants them honorary in-group status.

For example: Descartes has high enough status that the content of his saying "I think therefore I am" is more important to us than the fact that his actual words would have sounded like gibberish (unless we know French); people who speak gibberish normally have low status. Or, as Arnold Schoenberg once remarked (probably in German), "What the Chinese philosopher says is more important than that he speaks Chinese". Only high-status people like philosophers get this kind of treatment!