The docs on prudent mode have been already updated [1]. As for recommending that apps be designed to write to log files from a single process within the environment", although probably good advice, I don't wish to go that far. For instance, file locking works reasonably well for local files. I had done lots of tests on NFS mounted files when prudent mode was introduced and it seemed to work well. Recent tests in a different environment did not go as well. I think it's best to warn the users but let them decide for themselves. Do you think the warning in [1] is too mild?

[1] http://logback.qos.ch/manual/appenders.html#prudent