I don't think the reason for the rejected merge shows at the lower right of the page.
To prevent the merge being proposed over and over, it would be a good idea to include something in the biography, like a research note, to explain that so and so and whomever are not the same people because_____. Often rejected matches are undone because they are in error. Sometimes they should have been unmerged matches because they represent the same people, but death dates or parents need to be determined first.