Hi Ceki,
Have you considered customizing LevelConverter [1] ?
I followed your suggestions and implemented with success a customized LevelConverter. This solution for level names internationalization is of course less invasive than the one I devised (that consists in modifying the Level class). However, the use of the new conversion word for obtaining localized level names leads to higher computation time in the application I am working on. For example, running the application on an input that leads to the generation of about 63000 logging event, when using the conversion word level in patterns (1) the execution takes about 22 seconds, while when using the new conversion word for localized level names (2) takes about 66 seconds. Using the solution I devised (3) the application takes 46 seconds to terminate. The main difference I noticed between the three executions is the number of invocations to the method makePropertyResourceBoundle of the class CAL10NResourceBoundleFinder. For (1) that method is invoked about 500 times, and the execution times of these invocation sum up to about 34 seconds. For (2) we have about 19 invocations for a total of 299 ms. For (3) about 266 invocations for a total of 18 seconds. I still have to see what exactly that method does, however I find this differences in the number of invocations a bit strange. Cheers, Dario