To answer your question, there isn't a way to contact other users directly unless they provide details on their profile page.
Now if you leave a comment on one of their posts the new recent changes feature should alert them by highlighting the envelope beside their username at the top of the page.
To answer the question behind your question:
If you are refering to this answer from cozmicdad.myopenid.com then they appear to be using their OpenID as their username. Going to their OpenID endpoint you can see their name is Dave Russell, althought there's no other information there (even in the vcard).
Googling for Dave Russell found lots of dave russells, but not any that I thought could be the one you're looking for. Googling for Dave Russell Programming find this: http://www.liveperson.com/dave-russell-1/. It's not 100% certain, but I'd be pretty sure that's the same person. There is a send email button on that page.
Edit: Why the downvotes? I think I've found the guy he's looking for.
(I realise it's a bit creepy, but in this day and age we should be aware that this kind of thing is possible and not really that hard (it to me longer to write this answer than to find the guy). A reminder perhaps that we need to pay attention to even the smallest pieces of information we give out about ourselves.)