So you can track that person that keeps changing their username
Deep logging available, as per the bot description
Invite Logging with vanityURL support, Reaction Logs, Role Logs, Message Logs, and Image/Attachment Logs. Detailed logging show what invite code was used to join your server, and who invited them!
As well as allowing any user to post any emote, NQN allows moderators to create a special channel to log messages the bot has reposted.
Logs many servers into a channel named #bump
Mirai allows you to define an event channel where selected events are recorded. This allows you to have an easily visible log of moderation actions with their reasons. Username and nickname changes can also be logged.
Configurable logs, every action you'll know it even channel's permissions overwrites.
Wick will log anything security related in a channel of your choosing in the most detailed way possible. It also logs any moderation acction made.
Benny includes an advanced logging system that allows you to track everything that's going on in your server.
HaileyBot's '$-modlog' command will make her log all server activities to a designated channel, allowing you to know what happened on your server while you were away.