Following are a number of back-translations as well as a sample translation for translators of Proverbs 17:28:

• Kupsabiny: “If a fool keeps quiet, (it) is thought that (he is) wise
  and (he) is taken to be an understanding person when (he) does not speak.” (Source: Kupsabiny Back Translation)
• Newari: “Even a foolish person will appear to be wise
  if he remains silent.” (Source: Newari Back Translation)
• Hiligaynon: “Even the foolish are perceived-to-be wise and have understanding if they keep-quiet/silent” (Source: Hiligaynon Back Translation)
• Kankanaey: “Even the one who is mindless is as-if intelligent/wise if he remains-quiet.” (Source: Kankanaey Back Translation)
• English: “People may think that foolish people who do not say anything are wise;
  if foolish people do not say anything/keep their mouths shut, others will think that they are very intelligent.” (Source: Translation for Translators)