Obviously preventing people from sending or visiting URLs is a poor choice, and obviously some people want previews. Security isn’t stopping people from doing things, or even stopping them from doing insecure things; it’s stopping them from doing insecure things by accident or needlessly. @9er is right that this would need careful integration with existing functionality like proxying. A bot sort of does this; @Leanderl, does adding a preview bot to your chat not work for you?