Still having this problem. Anyone?Same problem here. Can't 'sign in' to youtube on safari. Works fine on Chrome. I've disabled any adblockers and emptied cache (all of it!) but still can't log in.
I finally upgraded to Sierra and now I can use Youtube on Safari just fine. Don't know what the major differences are between Sierra and El Capitan that would resolve this issue but, seemingly, it has.I haven't been able to see comments on YouTube for months. I have no idea why. I always have to open chrome or Firefox as well to see the comments.