Manual:$wgHideUserContribLimit

User rights, access control and monitoring: $wgHideUserContribLimit
The maximum number of edits a user can have and can still be hidden by users with the hideuser permission.
Introduced in version:	1.23.0 (Gerrit change 98267; git #8616f1b9)
Removed in version:	Still in use
Allowed values:	(integer) or false
Default value:	1000
Other settings: Alphabetical | By function

Details

A limit for performance reasons, to prevent a user with the hideuser user right from hiding a user with too many edits.

The limit can be disabled by setting to false.

To determine this, the database field user_editcount is used. See that page for more information.