Matrix is not a platform, it's a protocol and some implementation software developed in the open.
If the headline “(extremist group) use / flock to matrix to plan (nefarious thing)” shows up in the news, these distinctions hardly matter anymore.
https://www.express.co.uk/life-style/science-technology/6275...
Like Mastodon, Matrix has it built-in in its principles that a federated instance can prevent being contacted from another (this is the whitelist setting). Feel free to correct me, I am not 100% sure.
[0] or available for real money !
P(I use this | I’m a bad person)
because, like you point out, this obscures cases, like breathing air, where P(I use this) is already high. Instead, we care about
P(I’m a bad person | I use this)
And we especially care if this conditional probability is perceived to be high. This is because then your potential users will worry that if they use your product, others will make the (justified!) Bayesian inference that they are bad people. Because they don’t want to be seen to be bad people, they will avoid it.