I think most blog comment forms have a "website " field for a reason, though. There's a tactic quid pro quo there. Leave a comment, add value to the discussion, maybe a few people will click on your link. And the vast majority of bloggers I know are happy to get comments. A well-placed comment on an unknown or up-and-coming blog can make the author's day.
The impression I got (and the impression I get as a blog owner) is that he was leaving a link within the comment body, as opposed to the URL field. People do this all the time on my site and it sort of immediately invalidates their comment for me.
The question is only how relevant the link and comment itself is.