robogato, thanks for enabling multiple posts. It makes it a lot easier to have conversations through the recentlog.
Zaitcev, sorting topicality for different syndication points is what tags are for. Most blog software where generate tag-specific feeds, but it's not clear livejournal is among them. I'm not aware of a standard for including the tags in RSS items themselves, but there's an atom:category element that looks like it's for this. So maybe some combination of using a tag-specific feed from a blog and filtering by atom:category on the advogato side would work?