My understanding is that S3 can only serve without the trailing slash if you rename all your files and omit the .html - so if you have a file named
about and it has no extension, and it is an html file, it should be able to serve it and there will be no trailing slash or extension. There is no real way to accomplish this easily so I have not seen anyone do it. All my S3 urls have a trailing slash.
Keep in mind that S3 is not a server - it is a storage manager with the ability to serve files.
Also, I would think from a google search standpoint that you would not want both /about/ and /about to work - seems like they would be dupe urls?