Thanks for the comments so far. I have discovered a few things: 1) I really don't expect anyone except developers and maintainers to edit configuration files directly; I expect some program to manage "user" changes. 2) If I have a large file, I prefer XML with a DTD because it can help prevent size=blue or color=large type mistakes; that's good even if machine-generated in error. 3) Most of us agree that XML should be edited by good tools (presumably not just vim...).