Available from 19.3!
When commenting on the intranet, users are able to @mention, which allows users to "tag" and reference other users in comment fields. The user who becomes @mentioned will receive a notification if they have access to the content to which the comment is linked.
In addition to @mention, users have the opportunity to post a reply to a comment. This allows users to communicate in the comments without interrupting the 'flow' of the conversation. To reply to a comment, click the 'write reply' text on the right hand side of the chosen comment. From here, type in your comment as you normally would. You can tag users in your replies as well! Once finished, press 'Send'. Replies can be hidden as well, to reduce the space used by the comments.