It would be great if plugin authors will automatically receive e-mail about creating forum topic connected to his plugin.
If user downloaded the plugin, installed it and have some trouble with it - user creates forum topic about his trouble with this plugin by clicking the link "Write a new topic" at the bottom of the plugin's page. Or just clicks button "Broken" on plugin's page WordPress automatically helps user to create topic with details of the problem.
Plugin author is the person which knows this plugin better than everyone else and could answer better about troubles with it. The problem is that plugin author does not receive email about new topics about his plugin and maybe he will never see this topic and maybe user will never receive an aswer to his question.