The only way I think to achieve that is to combine some sort of revision storage with an automatic Sigil command logging function of some sort to provide the reason (culprit

) behind each change.
Even With a plugin and git/rcs/cvs system behind it, since these is no automatic sigil command logging, the user would still have to manually make a commit with a commit message explaining what commands caused the changes. So not what you want either.
Sorry.
KevinH