Some words or grammatical constructs are a clear indicator that the machine translated text is wrong, or are likely to be wrong. Often this is related to keywords, and if they exist in the source text for a specific language, then it is highly likely that the target text would need to be edited. Examples are such things as feminine gender prepositions in translations from Norwegian to Danish, and differences in perfectum and preteritum between Norwegian and Swedish. The later can be difficult to detect, but the former is pretty easy.
If there is an indication of a troublesome sentence, then the translator should at least check something (a check box, click on a menu entry) to show that he knows there is a problem with the text. One idea could be to make a hover dialog where he can accept the translation, otherwise he has to change the text to make it pass validation.
Given that I have source text fragment ei lærerinne (a teacher, feminine form)
When I try to translate that text from Norwegian Bokmål into Danish
Then I should be warned that ei is a problematic construct
See also T162524: Too many errors from the Yandex translation engine (possibly other engines too) but note that this problem is common in texts produced by all translation engines.