So I was browsing places and saw that no one has a plugin for this. So here is my idea. It would not be a banning plugin. However, it would be a plugin that when you ban someone, you can let it give you information. Like if you were banned, kicked, etc., the reason, and who you were banned, kicked, etc. by. Not only that, but in that plugin, allowing you to see the reasons for the bans, and who they were banned by. This would have to be non-SQL however.
Could do a local SQL Database, might make it easier. Pretty simple to do. Let me know if you can t get to this and Ill do it in a couple days after Finals.
This is already in bukkit. The /ban command actually has an arg. Reason. so if get your ops to do "/ban AidoP Banned by Iceman4391. No spamming!" or something it would be the same. If you mean an individual log, that would be cool.
Banning is built in to plugins like CommandBook, Essentials, AdminCMD, so just use one of these big ones. There is also UltraBans.