Erik Moeller wrote:
It is increasingly common that subjects of articles wish to interact directly with us and tell us that their article is wrong in some way. It is, in my opinion, silly for us to reject even harmless corrections on the grounds that they cannot be traced to a reliable source. If Wikipedia itself becomes a primary source in the process of someone commenting on "their" article, what is the problem with that from a purely factual point of view? Depending on the nature of the statement, such comments could be either incorporated as corrections (date of birth) or attributed statements (".. denies that he ever had sexual relations with that woman").
Because WP:V requires that challenged statements have sources. You can't replace one unsourced statement with anohter like that, nor would it be acceptable to replace a sourced statement with an unsourced one.
-Jeff