Hi there,

I am afraid that this is a known issue and it's on YouTube's end.

As part of our Support Community improvement project, we’re preserving inactive posts that have historical or community value and closing them to new comments. This is one of them!

If this post covers a topic that you’re interested in discussing with the community or requests a feature you’d like to see on Khan Academy, you can try to find an active post about it and add your thoughts (or feel free or create a new post if it doesn’t yet exist in the forum).