If you are uploading a video from your computer, you can use any video editor to rotate it beforehand. Don’t worry, the Videos section is still being improved. Our developers know that lots of users would like to see the rotate button again.
When you add videos that you’ve found using the general search to My videos, you’re creating a link to the original video, not making a copy of it.
When a user opens such a video, they will see the source video, with comments and likes from there. You aren’t able to edit any videos you’ve added from the general search (since December 28, 2014).