[chousuke]

The thing most people seem to miss is that you can't actually mutate a commit in git. You can only appear to do so by removing the old commit and replacing it, and all of its children if it has any, with new commits.

If someone depends on your "mutated" commit, they will notice that it's gone, and you can deal with the issue.

The most common use for rebasing and commit editing is to make commits actually sensible.

Huge end-of-the-day commit-all-my-work chunks do not benefit anyone. The index and rebasing allow you to create commits that make sense, regardless of the state of the working tree. In subversion, this is a painful, dangerous and error-prone operation that involves manually using diff and patch. Git frees the developer from having to worry about when to commit.