The blogger is Jinge of http://www.jinge.se/ (Swedish) These comments have been on Carl Blidts blog since early april, for over two months now. During this time it has has been mentioned to him several times. He has been interviewed on both the news and the radio about them, without removing them. It is probably more because of incompetence then malice because he on the news said IIRC that he wanted to remove the comments but there was no point in doing it since they already were in "the cache".
13000 comments is not much for a blog as old as Carl Bildt's. In comparison Jinge's blog has about 30000 comments all manually moderated before being visible on the blog. These particular comments were few and all in the same thread. The comments encouraged prosecution and/or extermination of the Palestinan people.
These laws are seldomly used, but have been used in recent yers agiants hate speech advocating prosecution of and/or violence towards jews and homosexuals, and probably others that I can't remember right now.