"retouching" is a term in translation studies, which refers to technical work such as grammatical modification of non-native speakers in cross-language work, and does not involve rewriting content, but only language services.
But I don't know who first used the word "retouching" and introduced it to people outside the industry, thinking that retouching is rewriting and an informal service.
In the scientific research service of the doctor of science and technology, polishing is a basic and necessary language aid. But in the field of liberal arts, because most people have no experience in English publishing, they often don't know what polishing is for.
The legitimacy of the revision of the paper is also reflected in the following two aspects: First, the periodical requirements. Most English academic journals explicitly require that papers whose English language is not up to standard should be processed by a third-party polishing institution and provided with polishing certificates from the third-party institution before they can be accepted.
Second, colleges and universities also have this requirement and special support. Schools will have special funds for cross-language academic publishing, and some schools will also bid for polishing papers. For the services used, a paper polishing invoice should be issued.
Therefore, it is absolutely legal to polish the paper, otherwise there will be no above two requirements. However, the academic service circle, like other circles, is indeed mixed, and it is not excluded that some people provide improper services in the name of polishing. However, this does not belong to paper polishing itself.
Therefore, when choosing a retouching company, you must choose a reliable one. Legal compliance of services is the first priority. For example, some large international publishing houses, because they are doing academic publishing, their polishing services will be more standardized.