Metacritic did something rather obscure that will do no favours to the integrity of their site, Death Stranding or potential users that will look for information before buying the game. Removing negative reviews is not a bad thing on its own but doing it silently definitely is.
Death Stranding went from 5.1 to 7.4 user score on Metacritic overnight. That is suspicious in itself and many are already raising theories about the game being groomed for The Game Awards but this is not necessarily true.
Considering that 2019 saw more review bombing incidents and even instances of positive review bombing , it's not really weird to see some reviews being removed. Steam even put together a feature to protect developers, publishers and games' image by filtering "off-topic" reviews , which usually happen during such events.
No one batted an eye when Valve did it, with the most likely reasons being that Valve were transparent about the feature while also allowing people to opt in or out of it.
Meanwhile, Metacritic decided to remove over 6,400 negative Death Stranding reviews silently. It is currently unknown whether they expected this to fly under the radar but it's hard to imagine they did.
Anyway, many of those review removals could be warranted due to coming on release day and barely any reason to for 0/10, reference the wrong game or just be toxic and not much of a review overall. Whatever justified reason may have been behind the removals, it will be now buried under the controversy caused by silence.
Keep in mind that each coin has two sides and just like there may have been unwarranted negative user reviews of Death Stranding, this may be the case with the positive ones as well. According to the thread that brought the removals to light , there were no major changes on the positive side.