It would be useful if the MDC keyword also has evaluator parameters just like the caller conversion word.

An example usage:
In a web application I store HTTP headers, parameters, URL into an MDC variable. This context information should be displayed with most log message. However there are a few types of log messages which are very frequent. Eventually (but it may take years) the reason for this messages are eliminated, but until then the long context information should be supressed from the log file. (In such cases the frequency or the existence of the event is the information, not the content of the event.)