Philip Allison - 2010-11-15

Ident "authentication" doesn't work with a transparent proxy. The protocol works by asking the ident daemon on the client machine for the name of the user who made a particular connection. The trouble is that, with transparent proxying, the client machine hasn't made a connection to the proxy server (as far as it's concerned): it made a connection directly to a webserver, which was intercepted without its knowledge. So when the proxy server asks it "who made this connection to me?", the ident daemon has no knowledge of the connection in question.

There is nothing that can be done to fix this. The solution, as you have already discovered, is not to use a transparent proxy. This is just one of many caveats of transparent proxies.