The filter protocol does not report a unique identifier to the message. When filtering a large amount of messages the filter protocol is useless because the log entries could not be related to a specific message. I propose that the filter protocol should report first the message id of the parsed message as a reference to the message.
Already fixed in 4.10 I added "const QString logText( i18n( "<b>Begin filtering on message \"%1\" from \"%2\" at \"%3\" :</b>", subject, from, date ) );" => we have subject/date/from so it's enough I think :)