it's an interesting point, that. should news aggregators consciously avoid paywalled articles, and if so, why? Do they increase the ratio of noise to signal her, because few people can benefit from them (hence they are pure noise to most people here)? That's quite the irony, since their entire selling point is that paywalled content is higher signal, lower noise.

Perhaps it comes down to the aggregator's audience. Some will be more willing to pay to get past paywalls, for articles recommended to them by that aggregator, or have a higher tendency to already be paying customers. Hence P(article recommendation will be appreciated) will tend higher there, because P(article will be viewable) is higher.