[swift-evolution] [Review] SE-0117: Default classes to be non-subclassable publicly

[Tino Heth]

> Forking is desirable if your goals, needs, values, etc are substantially different than the library author such that you do not agree on what the API contract should look like.
That's desirable in the same sense as an amputation that saves you from a deadly sepsis... I'd rather stay away from both situations.
Forking drains manpower from real improvements, and the same is true for trivial pull-requests that can be avoided in the first place by keeping the defaults as they are.