Comments on BitChute are currently handled by Disqus, and you can use your BitChute account details to post a comment. If you don't turn this feature on you would need to sign into another Disqus account before you can comment on videos.
To use your BitChute account for Disqus please go to Menu -> Settings;
Then select 'Disqus';
And tick the box and click 'Save';
Once you've this you'll be able to comment with your BitChute account details.