There’s an algorithm which KA uses to check comments for low quality. If you could find the correct format to score low enough, I’d assume it would be hidden until moderators could review it.

I believe comments with links to sites which aren’t on KA’s permitted list also get autohidden. Perhaps make a fake url, something like https://www.pleaseautohidethiscommentitsafakelink.com

Our discussions system uses an AI filter to detect low quality posts, but there's not a specific phrase (other than inappropriate words and off-site links) that you could use to auto-hide comments.

Posts that are auto-hidden like this are still reported to our moderators for reviewal, so I also don't suggest trying to create lots of auto-hidden posts, as this could lead to your account being suspended by our moderators or our AI system.

Writing your comment in all uppercase letters and then writing one word in lowercase letters like this:

OH LOOK THIS COMMENT IS ALMOST IN ALL UPPERCASE. end.

Will give your comment a low score and will get it auto-hidden.

But like Evan said that gets your comment reported to the moderators so don't do it. Maybe not all low-quality posts should be reported to moderators though. But then again I don't really see any reason for Khan Academy to change their current comment system; because what is the point of writing comments that nobody else can see? I can't think of any reason you would ever need to write a comment that is hidden from everyone else.

I think that Khan Academy should whitelist more sites such as 

https://developer.mozilla.org/

and

https://www.w3schools.com/

because those are two relevant sites that I use a lot to learn about functions that Khan Academy doesn't teach. And it's annoying to have space out the link like this

ht tps : //developer .m ozilla. org/

just so that I can send a person relevant and helpful information.

Another thing to note: Posts with spaced out links are still reported to us, and we usually edit them to use the proper clickable link (assuming the links are appropriate), so you'd might as well use the normal link anyways.

The spaced out links are sometimes immediately visible, but given that most answers are reviewed in < 24 hours and most questions aren't time-sensitive, there's really not a need to do this. We also don't want to encourage users to circumvent the security features, as they are there for a reason.