Clients can remove messages from reporting context

The 1.19.1 release candidate increased the number of messages sent as context in a chat report. However, since message selection is done entirely client-side (within the ChatReportBuilder class), it is possible for a malicious player using a mod or hack client to choose not to include messages that exonerate the victim. As long as the malicious player includes the correct number of messages, it is impossible to tell whether a report has been tampered with.