Here's a plug-in I've been running on my servers for months to aid my admins handle troublesome players.
The /mute command is a good way for admins to quiet down the more vocal players, however mutes are only temporary until a player leaves; so, many players will rejoin to bypass the mutes. In an attempt to reduce the number of bans on my servers for bypassing mutes, I wrote this plug-in to persist mutes across player joins until the mute functionality is rewritten in BZFlag itself.
All development for this plug-in occurs on GitHub, so be sure to follow development and new releases there; I will very rarely update this post with updates on new releases. The link below will always point to the latest stable release.
Plug-in Download (BZFS 2.4.12+)
[ GitHub | README | Download | MIT ]