Thank you for creating there doesn't seem to be any other firefox extension that does this.
It's almost perfect, I'd like to see the following improved.
- Tab buttons don't fit the theme of youtube, they could do with modernizing.
- Tab buttons apear over the tabs content
- Make it more obvious that you can resize the tabs section as I didn't look at the screenshot and at first thought it was stuck using the default view.

It works but reducing the comment section size also cuts the comments. if it can be improved, it will be at its finest!