@Nick, this isn't quite what I required in my case but for yours I would imagine you would first sort the DataView object and then apply the Datasource e.g. put the following in place of rptComments.DataSource:
DataSet comments = BlogCommentInfoProvider.GetPostComments(PostNode.DocumentID, !isUserAuthorized, isUserAuthorized, DisplayTrackbacks); //Data to be sorted.
DataSet result = null; //Declare a dataSet to be filled.
// Sort data
comments.Tables[0].DefaultView.Sort = "CommentDate ASC";
// Store in new Dataset
result.Tables.Add(comments.Tables[0].DefaultView.ToTable());
rptComments.DataSource = result;