It seems to be plausible to communicate in more detail what a link or image is about, or publish additional references. At the moment this has to be done in the comments. This sucks, because OPs tend to know more about their topic than average commenters, and also may want to steer the discussion in a specific direction, provide additional references, and so on. This should be done in a dedicated text-field, and not in the comments. So Link-posts should simply be a subclass of text-posts and have just additional fields.