I disagree -- retracting a comment just means “I regret saying this”, whatever the reasons for that.

OTOH, I think that as a matter of honesty one should still keep the original text of the retracted comment intact (possibly with an explanation for the retraction added), unless it is contains potential memetic hazards (even for readers who know the writer has disavowed it), discloses confidential information, or similar.

EDIT: Should have looked into this more carefully -- apparently he retracted the comment immediately after posting it. Yes, I agree that's improper. Retracting.