In France it's important to respect privacy in order to deal with CNIL recommandations.
SVN property svn:author
keep a trace of every person who has commited changes on the repository.
The Cnil's recommandations preconize to anonymize the information especially when time as passed and the information is no more interessant.
Svn's server tools comes with svnadmin
and svndumpfilter
but none of these can process svn:author properties.
svn propset
fonctionality can only deal with a local checkout of the repository.
More about svn propset