It has only happened twice, and we have undone the deletes no problem, but user is insisting it's not their fault. The biggest problem this could cause is mistrust in the SVN system itself or at least its logs.
They know how to delete files, they use tortoise SVN, and know that ticking a missing file in the commit dialog and commiting results in it being removed, but they insist that this is not the case.
Delete commits are always with changes in other files that are clearly them, so no one is impersonating them.
How can I prove one way or the other it is them or not without holding their hand during each commit?