Which action is judges prohibited from doing voluntarily?

Judges are indeed prohibited from voluntarily testifying as character witnesses because doing so could compromise their impartiality and the integrity of the judiciary. When judges take the bench, they assume a role that requires maintaining an appearance of neutrality and avoiding any actions that might suggest bias or favoritism. Testifying in such a capacity could create a conflict between their duties as judges and their personal relationships, as well as cast doubt on their ability to remain fair in future cases that may touch on similar issues.

In contrast, while judges are discouraged from certain activities, such as providing legal advice, engaging in public debates, or discussing cases in public forums, these actions can have varying degrees of permissibility depending on context, timing, and jurisdiction. For instance, discussing cases in public forums may be strongly restricted, especially regarding pending cases, but it may not be outright prohibited under all circumstances. Therefore, the specific prohibition on judges testifying as character witnesses highlights the unique concerns about maintaining judicial integrity and impartiality.