Someone repeating a bad idea of someone else's is usually evidence that they have poor judgement. If they would have had good judgement, they would have seen that the idea is bad.
But them telling you a good idea of someone else's normally isn't nearly as strong evidence that they have good judgement. (This is especially true if high-status people in their social circles have many good ideas.)
So there's an asymmetry there.
This is similar to another asymmetry that psychologists have discussed, namely that that negative acts (e.g. stealing) are more diagnostic of character than positive acts (e.g. giving to charity), because the latter may have ulterior motives.
Repeating good ideas is also less diagnostic, but the mechanism is different.
Now we of course often evaluate others based on what they're saying.
But sometimes they're just repeating a good idea of someone else, unbeknownst to us.
That can lead us to overestimate them, since, as per above, repeating a good idea is much weaker evidence of ability than generating a good idea is.
But interestingly, them repeating a bad idea normally won't cause us to analogously underestimate them.
That's because, again, repeating a bad idea is in fact good evidence of poor judgement, just as generating a bad idea is.
