If half the reviews in question say something along the lines of “jacksepticeye brought me here,” it would definitely be the same question.
None of the criteria/examples I listed are exactly definitive. That’s why I brought up the Anthem example; you could end up with a ton of reviews saying something along the lines of “I love Mass Effect!” I’d argue that you’re going to end up with a lot of useless reviews no matter what you do, and I’m sure you’ve winced at the accursed checkbox-list-of-categories reviews enough times to know there’s some truth to that claim.
This is definitely a weird case, but there’s a few things that lean me towards saying this remains on topic. First of all, it is directly tied to Unity. If we saw people review-rocketing Rainbow Six Siege, Ghost Recon: Wildlands, and Watch_Dogs 2 with praise for the company’s response here, it would make sense. Even AC Origins and Odyssey would be crossing the line. With Unity, though, it is at least tied into the fact that this game has Notre Dame represented physically, making it actually relevant in this to begin with.
Obviously there is a grey area involved, and this can’t be remedied-- you will always have a little bit of debate here, like when Metal Gear Survive got slammed over Kojima’s zero involvement and Umbrella Corps was laughed at as a part of the Resident Evil/biohazard IP. You can argue they aren’t 100% explicitly part of the game, but they still hold some relevance to the overall experience, so it may just have to slide. I feel that Valve has backed themselves into this corner by claiming that DRM isn’t on-topic; it draws that line of intervention a little far forward, and blurs the lines between what does and doesn’t involve a game.
I’ve been concerned about reviewbombing as a concept for a long time, as far back as when I noticed some reviews on games that would downvote it for something related to, say, a sequel with a weird preorder bonus. For example, imagine reviews on the Arkham games, downvoting Asylum and City for the rough launch that Knight had. It wasn’t enough people to make a dent, but the fact that it happened at all in some franchises was concerning. This is the kind of thing the system seems to be made for-- it’s to make sure that what happens in a single game stays in a single game. Its intent was obvious-- Denuvo reviewbombs, Epic reviewbombs, and the like. Trying to stop some positive press for a game that is at least tangentially related feels like Valve would be pushing it a bit, considering how the this system was already a bit controversial (“stop censoring users!”).
So, there’s where I’m going to draw the line. If Assassin’s Creed 1-4, the Ezio spinoffs, Liberation, Syndicate, Origins, Odyssey, the Chronicles series, or any other Ubisoft title saw a sudden spike in review scores, and a large percentage of it was for this reason, it may be time to take action. Otherwise, as long as it’s contained to AC Unity, I’d say it should pass this time around because it still holds some relevance to the game’s context. Valve should definitely develop some kind of plan for a scenario like this in the future, if they don’t have one already… but action in this case might not be warranted unless it reaches beyond Unity.
Small sidenote: Having all these names on paper together, I can’t believe just how many AC games there are so far.