Quick note about future development. I don't have an up-to-date Flarum install at the moment so if you're having issues with this extensions, try fof/formatting instead.
gameox Not sure what you mean but I don't think that's a feature, no.
Night Sometimes, Flickr change their markup and make it impossible to extract the real ID from the page. If you can't embed a shortlink, try again with the long URL. Gfycat changed their embed URL a little while ago. You're going to have to wait for the next release of the s9e/TextFormmater library and for the update to reach Flarum.
neogeo You can post about it here. I have no immediate plans to develop this extension further but I'll consider it for long-term changes.
JamesGary Sorry but maintaining site definitions for websites in Chinese is too much work for me.