MC-253888 is a very worrying bug that has been marked as working as intended. One can imagine malicious servers which modify a user's chat with the intention of banning people.
The official line from Mojang seems to be that players should proof read every chat before sending it. Unless players are made aware of this exploit, why would a player be so diligent? Most players will not be expecting this, especially children. So why would they proof read every chat before sending, with the intention of finding maliciously altered text?
Even if they are notified, most people won't be this dilligent. Or maybe they'll forget to at some point.
This seems to be a serious issue and I would appreciate a response from u/xilefian or u/sliced_lime or similar.
It also seems like a Jira mod has a satisfactory solution, which retains the intention of this f...