I'm late here, but personally I would have liked that idea. And indeed I have local patches for including filename, line, return address and other information in each log line. In particular, I find it helpful to have filename and line to quickly locate where the logging site is, even when I am dealing with parts of Wine I'm not too familiar with. Sometimes I've used the return address to distinguish between calls made directly by the application or resulting from other Wine code. I find that helpful to quickly understand what the application intention is, independently of what then happens because of Wine.