We changed the default mouse click behaviour to double-click for KF6.
For me this was surprising, so I would like to raise a few questions here that might as well be answered with: "sure, we are", and I just did not see it because I am a bit out of touch with KDE development news (and modern ways of communication in general). Personal and biased opinion follows. But here are the questions first:
Are we handling such a prominently user-facing (as in in your face) changes transparently enough?