What I mean is - do search engines treat the index file in a folder as a file that can be indexed?
User agents have no idea what your "index" page is actually named, they just request a URI and the server sends a stream of data as a response
What if you have internal linking that links to both the folder level AND the index.html - would that be considered as being two seperate files?
The only thing to understand is that search engines index URLs, and if two or more URLs return the same document it IS
OK - but just to be 100% - are you sure that this will create a re-direct loop?
( I am placing the below index.html into "new folder" )
redirect 301 /old-folder/index.html http://www.my-site.com/new-folder/
That won't cause a loop, redirecting /folder/index_page_name.ext to /folder/ will.