Description:

In Admin UI - Message we have Message Erasure Type option.
Default is Delete All Messages
But if you set Keep Messages And User Name - you get same behavior and Delete All Messages set - all users messages are deleted.

Steps to reproduce:

1. Set Keep Messages And User Name value in Admin UI - Message
2. Delete user that had messages in DM and other chats
3. No messages of deleted user remain

Expected behavior:

User account should be deleted, but messages in chat history should remain and be authored as deleted user (when that user was on server, for example UserA @usera)

Actual behavior:

Server Setup Information:

• Version of Rocket.Chat Server: 4.2.0
• Operating System: CentOS7
• Deployment Method: docker
• Number of Running Instances: 10
• DB Replicaset Oplog: Enabled
• NodeJS Version: 12.22.1
• MongoDB Version: 4.2.17

Client Setup Information

• Desktop App or Browser Version: Chrome 96
• Operating System: Windows 10

Additional context

Tested on 3.18.3 with same result

Third option look like work fine

Relevant logs: