YouTube – What Does sub_confirmation=1 Do?

There is no purpose to using the feature parameter in a YouTube embed link nor do I think you should be using that when embedding. When embedding a video YouTube actually has a different URL they use in the src field.

For example with the video link you are using your src field would use this url: http://www.youtube.com/embed/275VsDVauN8

When on the video's page you can click share and then embed and be presented with the options for embedding and the code you would insert into your html document to embed the video (see image below)

Using this tool on the share page should provide you with what you need to embed the right way. The feature parameter is not used in embedding.

This exact question was answered in a post by a user named "ytKeane" who is a Google employee:

It means that your video isn't live yet. With the changes we made to the uploader this week, if you have a public video that's been uploaded, you need to "Publish" it before it goes live to your subscribers. Public videos that haven't been published are in "draft". In Video Manager there should be a big blue Publish button next to videos that have not been published.