We updated the editor in the Chatter publisher for enhanced security and faster performance. But they’re not the only benefits. For one thing, you now have styles, images, and formatting in comments and answers. For another, mentions work more efficiently in the new editor. When you start to mention someone, the selection list opens right where your cursor is instead of at the bottom of the publisher. Topics gets the same treatment. When you add a topic to a post, the topic selection list opens at your cursor rather than at the bottom of the publisher. This feature is available in Lightning communities.