If you are putting audit trail in source code, merging changes from one release to another becomes a chore. Since there are no trivial merges anymore. You get c

If you are putting audit trail in source code, merging changes from one release to another becomes a chore. Since there are no trivial merges anymore. You get conflicts in comments which have to be merged by hand. Also without ability to diff files, you are never sure what actually changed for a given comment. So you are dependent on VCS anyway! I have been burned by this in two large codebases (> 2k files).