How to "Reply To" messages from an archive?

Suppose I wanted to reply to a message from the archive, e.g.:

http://lists.w3.org/Archives/Public/public-lod/2009Dec/0145.html

If I did not get that email, how can I do this?

As  workaround, I suppose I can copy and paste the message and make it  look
like a reply, and if I get the subject right it may go into the right
thread.

Thanks
Michael