Overloading the word 'censorship' is going to get a bit confusing here ;)

"Censorship", meaning: "malicious server or ISP silently blocks or withholds traffic from you" is a risk in Matrix today, completely independently of the reputation stuff being discussed here. The mitigation is to get rid of servers (and even ISPs), as per https://matrix.org/blog/2020/06/02/introducing-p-2-p-matrix/

"Censorship", meaning: "your server admin subscribed to a blocklist of child abuse content published by someone like iwf.org.uk" would stand out to users by the server publishing the names of the blocklists that their server admin has deployed. I'd call this server-side filtering or something instead, given the filters are visible. If the server admin withholds info about their filters, then you're back in the traditional sense of censorship from the prior paragraph.

Are the blocklists public? I thought these schemes involved uploading files to a "trusted third party" like Microsoft, and for them to decide if the files are lawful?