Has anyone successfully used the undocumented addcomment XMLRPC method?

It seems to take journal, ditemid, parenttalkid, poster, body, subject and props.

ditemid is self-explanatory, but I'm not sure what parenttalkid is. Every time I've tried to call the method, I get an error of 'No such entry. at /home/lj/cgi-bin/ljprotocol.pl line 250'. Looking at the code, this is right after the journal specified by the journal argument is pulled from the table. Any ideas?

Hello, please, help me to download all comments from community. I use perl-script with clear-authorisation in a LJ-server (XML-RPC). Community is very big and old. And method syncitems get me 500 items. But I iterate this method and get all posts. Next step - is a downloading comment. In this step I got error. And autorisation is Faild. I create request to LJ whith method sessiongenerate and can get SESSID then send this ID to /export_comments.bml?get=comment_meta&startid=$maxid&authas=$SESSID Server response Error-content whith:
<h2>Error<h2>
...
<li>You could not be authentificated as the specified user</li>
...

But if I run this perl-script whith another autentificated-data (another community, no so big) I successfully get my XML from this URL.

Please tell me wrongs.