God I loved kparts, but wasn't that more the idea that everything should be embeddable?
> KPart technology is used in kde to reuse GUI components ... By using kparts in applications developers can spend less time implementing text editor or command line features, for example and just use a katepart or a konsolepart instead.
Yes it is, but since "KDE 5" I've seen less of it. Besides the obvious example of Konqueror another great example of it was reKonq, which used Akregator, Okular and Kget to handle RSS and PDFs respectively (all within the reKonq window).
Just from the top of my head that I've noticed as a user: several apps, such as Dolphin or Yakuake, use konsolepart; KWrite uses katepart, and Ark uses various parts in its file preview.
> KPart technology is used in kde to reuse GUI components ... By using kparts in applications developers can spend less time implementing text editor or command line features, for example and just use a katepart or a konsolepart instead.
https://techbase.kde.org/Development/Tutorials/Using_KParts