Merge should ignore all references to renamed item.
If a method, field, or property is renamed, the tool understands this and lets you know it was just a rename. However, it still flags every place in the code that references that item as a change. This seems like a simple thing for the tool to recognize and filter these out.
Renames (especially in Visual Studio) are done in an almost guaranteed bug free way. So, I would love to not have to see them in diffs at all.