the automatic chat censoring system is completely broken

I would recommend uploading the latest.log file from the client that cannot send chat messages, for extra debug information.

In addition, are you running a vanilla server? You seem to be describing an issue with a feature of modded server software ("automatic chat censoring system").

I have attached the player's log, they were using the optifine client (which i seriously doubt has any effect)
The server is a realm, so it literally couldn't be more vanilla

I also do not have the player blocked in the 'p' menu

I find it incredibly weird that this issue is occurring before 1.19.1 has even been released

they were using the optifine client (which i seriously doubt has any effect)

Optifine very much affects the client, please reproduce this without any mods.

Does this affect the vanilla game? Please attach a screenshot of this issue occurring with the F3 screen enabled, without any modifications.