From the product's homepage:
Kompare is a GUI front-end program that enables differences between source files to be viewed and merged. It can be used to compare differences on files or the contents of folders, and it supports a variety of diff formats and provide many options to customize the information level displayed.
Comparing directories Reading diff files Creating and applying patches
It even allows a three-way comparison.
There are probably other applications with a GUI that my provide the same functionality, but KDE Plasma users may prefer, as I do, to use a KDE/Qt application when on Plasma and with a similar level of functionality/(complexity) as other KDE applications.
If this is included, there will not be a style or design paradigm/philosophy clash with the Plasma desktop or other KDE applications.