Two things. First: If you want to do anything on a WordPress.org blog then you're posting to the wrong forum. This is WordPress.com, you need WordPress.org for self-hosted blogs. Here's the page for the wordpress.org forums:
and to understand the difference between wordpress.com and wordpress.org, click this:
There are a couple of links at the bottom of that page that'll give you extra info too.
Next, if you need to comment on a self-hosted blog, you shouldn't need to log in unless you have a contributor role on the blog. Instead, you should just click the 'comment' button on a post or page there and comment as usual. So if you use the home URL which for the website you've given would be this: http://www.negativland.com that'll take you to the site itself.
I had a look though and most of the comments there are closed. As there isn't a contact page it appears like the blog admin doesn't want anyone to contact them. Can't help any more than that.