1 files changed, 39 insertions, 2 deletions

diff --git a/doc/user/discussions/index.md b/doc/user/discussions/index.md
index 4d6cff96169..7831fdff249 100644
--- a/doc/user/discussions/index.md
+++ b/doc/user/discussions/index.md
@@ -34,6 +34,20 @@ You can create comments in places like:
 
 Each object can have as many as 5,000 comments.
 
+## Mentions
+
+You can mention a user or a group present in your GitLab instance with `@username` or
+`@groupname`. All mentioned users are notified with to-do items and emails.
+Users can change this setting for themselves in the
+[notification settings](../profile/notifications.md).
+
+You can quickly see which comments involve you, because
+mentions for yourself (the user currently signed in) are highlighted
+in a different color.
+
+Avoid mentioning `@all` in issues and merge requests, because it sends an email notification
+to all the members of that project's group. This might be interpreted as spam.
+
 ## Add a comment to a merge request diff
 
 You can add comments to a merge request diff. These comments
@@ -90,8 +104,10 @@ An icon is displayed on the image and a comment field is displayed.
 If you have ["reply by email"](../../administration/reply_by_email.md) configured,
 you can reply to comments by sending an email.
 
-- When you reply to a standard comment, another standard comment is created.
+- When you reply to a standard comment, it creates another standard comment.
 - When you reply to a threaded comment, it creates a reply in the thread.
+- When you [send an email to an issue email address](../project/issues/managing_issues.md#copy-issue-email-address),
+  it creates a standard comment.
 
 You can use [Markdown](../markdown.md) and [quick actions](../project/quick_actions.md) in your email replies.
 
@@ -145,7 +161,7 @@ For issues and merge requests with many comments, you can filter the page to sho
 
 1. Open a merge request's **Discussion** tab, or epic or issue's **Overview** tab.
 1. On the right side of the page, select from the filter:
-   - **Show all activity**: Display all user comments and system notes
+   - **Show all activity**: Display all user comments and system notes.
      (issue updates, mentions from other issues, changes to the description, and so on).
    - **Show comments only**: Display only user comments.
    - **Show history only**: Display only activity notes.
@@ -155,6 +171,27 @@ For issues and merge requests with many comments, you can filter the page to sho
 GitLab saves your preference, so it persists when you visit the same page again
 from any device you're logged into.
 
+## View description change history **(PREMIUM)**
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/10103) in GitLab 12.6.
+
+You can see changes to the description listed in the history.
+
+To compare the changes, select **Compare with previous version**.
+
+## Change activity sort order
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/14588) in GitLab 12.10.
+
+You can reverse the default order and interact with the activity feed sorted by most recent items
+at the top. Your preference is saved in local storage and automatically applies to every issue,
+merge request, or epic you view.
+
+To change the activity sort order:
+
+1. Select the **Oldest first** (or **Newest first**) dropdown list.
+1. Select either oldest or newest items to be shown first.
+
 ## Assign an issue to the commenting user
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/191455) in GitLab 13.1.