When someone uses chat, their messages disappear forever once they quit, with no evidence of what they said remaining. This is a huge problem.
On Ben 10 Fan Fiction there have been at least two huge arguments since I've been an admin over something that happened in the chat, one of which nearly tearing the wiki in two and driving away a good writer. None of them have been truly resolved to this day because there's no proof for either side's stories. It's always "You trolled so we banned you and then you socked so we banned you permanently!" and "No I didn't, I said 'Hi' and was banned!" thrown back and forth with no resolution.
On Minecraft servers, however, everything in the server console—chat, commands, server messages, etc.—is dumped into a log file for the server owner to use for, say, resolving arguments or looking back to find errors. Something similar should be done here.
Everything in chat, even private messages and join/leave messages, would be put into Special:Log/chat, much like the others: one entry per message. It would only go back a month or so before the data would start being deleted. Private messages would be included because a lot of the issues happen in PMs, which not only does nobody have any proof of, but only two people can see! However, to make up for this, only admins and above can view this log.
This would be very practical for ending arguments, as it can save someone from being banned over an argument, and can also get people banned if they were lying about not doing something bad. I hope the staff consider this, and that it doesn't end up like my other ideas. :P
---****--- Roads 17:19,2/12/2013