When using multiple items with use excerpt set to true, the items are displayed on the main module using only the excerpt portion and the title of the iterm is the link to the full article.
In this mode the HtmlEdit.aspx page will show a field for the excerpt so it can be specified, but if left blank it will use a portion of the main content to create an excerpt.
If use more link is true then instead of using the title of the article to link to the full article, a more link will appear at the end of the article. and an edit field for the more link will appear on the HtmlEdit.aspx page. The idea was that this could be used to link to a full article on another site.
I will revisit this functionality when I get to improving the module as a whole. At that time I will decide whether this feature should be improved or removed. At the moment I'm leaning toward removed but I defer the final decision until I get my brain wrapped around working on that module.