That is expected. You need to implement additional customization to rendering HTML with Javascript or other means.

Overlay [1] for the method syncValue & replace [2] with [3].[1] /libs/cq/ui/widgets/source/widgets/form/RichText.js[2] this.el.dom.value = html;[3] if(this.el.dom){this.el.dom.value = html;}

Configure the limit to -1 for unlimted.  Some customer have internal policy for links not to exceed & hence made as configurable option. P.S:-    I am not moderator & do not have permission to set as solved myself. 

The implementation to make it configurable is complete & unfortunately did not make into 5.6.1. Will ship in next release. As scott recommended please file daycare with business impact.

Are you sure you are doing at [1] ?  Which version of aem.[1]   /libs/granite/core/components/login/login.jsp

That's strange.  Are you using any custom plugins.

Looks like you might have hitting the instance through webserver. Make sure mime type is set in web server.

Set boolean property hidden to true under /content/mac/jcr:content  & this should be fixed in next release.

If you are using latest AEM version & want this option for all PDF. You can backlist at [1] & which forces the file to download.[1]  http://<host>:<port>/system/console/configMgr/com.day.cq.dam.core.impl.servlet.SafeBinaryGetServlet

Disable the agent if you are not using it.