In general, whatever links you post to content, be aware that the original source does not have the same protections as this site. For example, a mega.nz link.
Putting links to discord images can result in those image links being reported. Then not only will the images get removed from the platform, but the user account also punished for that image. Please re-upload the image somewhere else if you ended up finding it on discord originally.
For a supported list of websites that automatically embed from a link, please look at this WordPress article: