This has been proposed elsewhere awhile back (2009?). I could not find any movement on it. I'd be interested in doing the work, if need be.

Au contraire, KInfoCenter modules were part of KControl (the former System Settings) in KDE3 times, and were explicitely splitted into a separate application, because they did not make sense in System Settings.

*** This bug has been marked as a duplicate of bug 187154 ***

Well, "make sense" is a purely subjective statement as can be inferred from the previous bug you kindly provided.  Reading the comments, it is fair to say that the discussion was hardly conclusively resolved.  In any event, since that discussion in 2009 we can find within the System Setting a clear divergence from the purist view point that only configuration items shall be present and that information items must be separated.  In fact, this purist view point flies in the face of so called "best practices", the feed back principle, and ergonomics.  The following items found in the current System Settings support my position (it may be skewed as I use Kubuntu):

* Account Details: Password & User Account: User ID - Relational information
* Application Appearance - Various visual feedback information items (based on the settings)
* Shortcuts and Gestures - Often used to find the keyboard shortcut, NOT to change settings
* Desktop Effects:  All Effects: Information button - Pure Information, also same as "Shortcuts and Gestures"
* Workspace Appearance - Various visual feedback information items
* Workspace Behavior: Activities: Plugins: Information button - Pure Information
* Bluetooth Adapters: Adapters - Pure Information
* Color: Devices: (Any Device): (Device): Information tab, Metadata tab - Mostly pure information (Metadata is pure information)
* Display and Monitor: Display Configuration: Information button - Pure information
* Display and Monitor: Screen Locker: Mini-display and Test button - Feedback information
* Input Devices: Joystick: Position, Buttons, and Axes - Feedback information
* Printers: Name, Location, Kind - Relational information
* Multimedia: Audio and Video Settings: Backend: lower panel - Pure information
* Font Management: Font Preview panel - Pure/Feedback information
* Startup and Shutdown: Service Manager: Load-on-Demand Services panel - Pure information
* User Manager - Without SU, user data is pure Information (sans self)
* Adobe Flash Player - all of the "Learn more..." links - Pure information
...and the most damning of all...
* About System - pure information 

We may rightfully argue that many of these information items are present due to the close correlation to the settings they represent.  Correlation is a tricky, subjective argument.  For quite a few items, we can easily argue that they "do not belong" PERIOD.  Yet, they do.  In my mind, these items do not detract from the core philosophy of "System Settings" as the information represents the System and its Settings.  These information items provide the user/administration valuable insight about the system so that the user/admin may make intelligent decisions about the configuration/setting for the system.

KInfoCenter does precisely that--it provides to the users/admins information to base a variety of decisions about the system.  IMHO, combining this information in the System Settings does nothing to detract from that objective.  To the contrary, it enhances that process.  In fact, System Settings + KInfoCenter provides a good audit of the entire system: hardware, software, and its configuration from the DE viewpoint.  Its certainly not perfect as many configuration items are missing, such as service configuration files.  However, those items can be seen as functionality deficiencies that should/could be provided by those developers for System Settings.  The Adobe Flash Player item is one example.

Another argument is for simplification.  The myriad programs used to interrogate, audit, and configure the system is reduced.  User don't need to search far and wide to find the "proper" tool to install and manage the system.  What is KInfoCenter good for if it isn't for allowing a user to gather important information to make configuration decisions whether they be System Setting changes or hardware changes?  KInfoCenter is a feedback mechanism as it helps a user/admin make configuration decisions.  A unified system simplifies management, enhances productivity, and reduces frustration.

We also don't need to be monolithic about the issue.  Based on the install choice, each system panel may be present or not depending on your viewpoint.  The KInfoCenter "panel" could be present in that program, System Settings, or both.  This opens choice to the user.  An ideal solution would be to place it in the About System KCM as a subpanel, link, etc.

Should we really resurrect the older bug?  Yes, its relevant, but the last entry was 2009 and System Setting has significantly moved on since then, i.e, toward inclusion.  As the previous bug was CLOSED, I humbly ask and welcome additional comment and insight on this duplicate bug.  Otherwise, I'll move this comment to that bug.

Regarding "About System", this module is not part of the KDE software collection, but a distribution-specific add-on. I suggest to report this issue to the bug tracker of your distribution.

All other items allow changing settings.