Expand comment and description info

- Also mention epics
- Add the number of characters (1 million)
- Mention that this limit might be changed in the future

doc/administration/instance_limits.md

@@ -19,6 +19,18 @@ will fail.
 
 - **Max limit:** 5.000 comments
 
+## Size of comments and descriptions of issues, merge requests, and epics
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/issues/61974) in GitLab 12.2.
+
+There is a limit to the size of comments and descriptions of issues, merge requests, and epics.
+Attempting to add a body of text larger than the limit will result in an error, and the
+item will not be created.
+
+It's possible that this limit will be changed to a lower number in the future.
+
+- **Max size:** ~1 million characters / ~1 MB
+
 ## Number of pipelines per Git push
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/issues/51401) in GitLab 11.10.

doc/user/group/epics/index.md

@@ -350,14 +350,6 @@ You can [award an emoji](../../award_emojis.md) to that epic or its comments.
 
 You can [turn on notifications](../../profile/notifications.md) to be alerted about epic events.
 
-## Limits
-
-This section gives an overview of limits of Epics and an overview of their background.
-
-### Description and comment length
-
-See [Issues: Description and comment length](../../project/issues/index.md#description-and-comment-length)
-
 <!-- ## Troubleshooting
 
 Include any troubleshooting steps that you can foresee. If you know beforehand what issues

doc/user/project/issues/index.md

@@ -201,18 +201,3 @@ Feature.disable(:save_issuable_health_status)
 - [Issues API](../../../api/issues.md)
 - Configure an [external issue tracker](../../../integration/external-issue-tracker.md)
   such as Jira, Redmine, or Bugzilla.
-
-## Limits
-
-This section gives an overview of limits of Issues and an overview of their background.
-
-### Description and comment length
-
-> Introduced in [GitLab 12.2](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/61974).
-
-Descriptions and comments on [issuable](../../../development/issuable-like-models.md) can be no
-longer than 1 million characters.
-
-Previously, there was no limit to issuable description size, which created a
-[possibility of a DoS attack](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/61974) by allowing
-very long descriptions. It's possible that we will set this limit to a lower number in the future.

doc/user/project/merge_requests/index.md

@@ -124,11 +124,3 @@ There are two main ways to have a merge request flow with GitLab:
 1. Working with forks of an authoritative project
 
 [Learn more about the authorization for merge requests.](authorization_for_merge_requests.md)
-
-## Limits
-
-This section gives an overview of limits of Merge Requests and an overview of their background.
-
-### Description and comment length
-
-See [Issues: Description and comment length](../issues/index.md#description-and-comment-length)