I mean, can I use it to hide an answer from my question or a hidden hint? Of course without showing it on the post.
There're people use this method. I've been looking for this but got nothing.
Sorry if duplicate. Thanks.
After you have inserted an image into your post via the Image interface, the image is already available on i.sstatic.net; you do not have to submit your post for that.
Therefore, you can just
The link to the image looks like this:
[![image description][1]][1] // image and link (default)
![image description][1] // image only
[link text][1] // text link to image
[1]: https://i.sstatic.net/vBb38.png // image URL
It is enough to delete the reference, but if you leave the URL, people will be able to see it when they edit the post. (That's also something people like to do: hide stuff in the post's source code. It's not something I'm very fond of, though.)