As Eric Kepes points out here http://dotnetjunkies.com/WebLog/ekepes/archive/2005/02/18/55346.aspx
This means there is absolutely NO need whatsoever to check in code with large blocks of code commented out. I think “change-log” style comments that appear at the top of code files are also un-necessary for this reason. Tracking who changed what and when is the job of source code control systems, not crufty code-comments.