Instead of changing the border size default for all KDecoration plugins by
switching the default from border size Normal to None introduce new
functionality, which allows a KDecoration plugin to recommend a border size in
its metadata. By default KWin listens for these recommendations and sets the
border size accordingly.
If there is no metadata recommending a border size, KWin falls back to the
current setting of Normal sized borders.
A user is able to override the recommendations from the KCM, which has been