Valve‘s blog post explained how Steam plans to change the negative reviews, which might be even unfair here and there.
In short, they will „identify off-topic review bombs, and remove them from the Review Score.” How will this happen? Let the blog post explain it: „We define an off-topic review bomb as one where the focus of those reviews is on a topic that we consider unrelated to the likelihood that future purchasers will be happy if they buy the game, and hence not something that should be added to the Review Score.” The Review Score term is effectively the percentage of positive reviews for a game.
However, even Valve itself admits that this area is grey (but they include DRM and EULA-related negative reviews), which is why they created a tool which „identifies any anomalous review activity on all games on Steam in as close to real-time as possible.” If it finds something suspicious (tons of negative reviews in a short period – last time, Taiwan-developed Devotion got a ton of negative reviews from Chinese Steam users for not directly, but still criticise Xi Jinping, their president), Valve gets alerted. If they find the activity as a review bomb, they notify the developers, and in the affected period, the reviews get taken out from the Review Score, but they will remain on the site – the devs can decide whether they want to keep these reviews or not.
The issue here is that every review would get wiped from the affected time frame, including harmless, even positive ones. The devs can opt out of the program, though. Still, the coin has two sides, and Gabe Newell might not have found both of them.