In a backshifted sentence for reported speech, we don't backshift the contents of a when-clause if the time relative to now has not changed:
"We will have a barbecue when you come" - the visit is in the future
He said that we would have a barbecue when I go - the visit is still in the future.
He said that we would have a barbecue when I went - the visit is in the past.
Looking at your sentences:
"The world laughed when I told what I had seen." - telling is in the past
He said that the world had laughed when he told what he had seen. telling is still in the past
As Jam Kay said, we generally avoid using past perfect if it's not strictly necessary. In your sentence, I think that it is necessary to distinguish between these two cases:
"The world laughs when I tell what I have seen." - still happens
He said that the world laughs when he tells what he has seen. -still happens now, afaik
He said that the world laughed when he told what he had seen. - still happened when he spoke to me
"The world laughed when I told what I had seen." - no longer happens
He said that the world had laughed when he told what he had seen.