One more idea to throw out there before I pass out. Which as @enso pointed out makes little difference since somebody has taken it upon themselves to implement this already.
A slightly more reasonable approach I think is to hide post by content. If it uses certain words, or relates certain concepts, then it gets filtered. The difference being that it does not tie people to “identities”. I love the guidelines of BB - apart from the fact that they are deliberately vague and enforced capriciously. And one of the great failings there is that everybody who participates there agrees to criticise the idea rather than the person - a very civilized notion - yet there is a lot of resistance to this, which is largely accepted by the staff. (How can one respect the rules of those who don’t respect their own rules?)
My experience is that accurate or helpful information can come from anywhere. The answers to how to cool your CPU, plant ginger, filter water, or patch your own genes are not dependent upon coming from a certain organism. What matters is that they work. And I see being attracted to or avoidant of an “individual” to function more as a form of emotional rent-seeking. Looking for an excuse to help or hinder others, rather than to be harmonious or out of social duty. But a person “is” ultimately only what they do. In my version of the real world, ecology comes first, then lifeforms, then one’s species, one’s family/commune, and then one’s “own person”. Why? Because each is a subset of the former, and like it or not, none can exist without the larger more fundamental unit. So having an individual want or worry that is more significant than the larger whole is somewhat destructive.
So even though hide post by subject would yield some ignorance, some blind spots in knowledge, it would not be essentially selfish in nature. A person might imagine that they are hiding info out of some sort of individualistic self-interest, but 1. they really aren’t, and 2. at least they are not pressuring other people into individualism by shaping the discourse of the group around personal identity.