Not only is it important when it is stated explicitly for such reason, but it is also important to know what group particularly "believes" it is so important. Also, it is important not to state the cart before the horse in such instances.
It appears these notions are known in practice, but it isn't covered in depth on guidelines. I wonder if it is possible.
Jonathan
Fastfission wrote:
And an easy way to even get around it is to make it an instance of reported speech.
"Joe wrote in his diary that he saw the ghost" -- let the reader parse out, if they want, whether he was just being silly or not. If Joe happens to be someone whose belief in spiritualism is important to state explicitly (i.e., Alfred Russel Wallace), then it is likely a secondary source has already commented on it.
FF