Yeah, I largely agree. Is that unusual these days? :D

And I'd be sort of okay if dicts implemented set operators, although I don't think using `set()` or `.keys()` is a big ask. But using the pipe operator for the operation in this PEP would be a bad idea IMO: For sets, a | b == b | a. For dicts, not necessarily. So if they used the pipe operator, that could lead to surprising or unintuitive results.

On the plus side, not using pipe still leaves it open for future usage, so you might get your wish yet.

Your exact point that for sets, union operator is commutative while for dictionaries it wouldn't be is one of the main objections I foresaw if I ever wrote this up as a PEP. Counterpoint: for numbers, + is commutative but for lists it's not, so it's normal for the same operator to have different commutativity depending on the type of the operands. IMO it's worth using the set operators because of the subclass relation of sets and dicts despite some small (but really, predictable) changes in behavior, but I can see how someone could have a different opinion.

The extension operator still resembles more a set union than an addition. The fact that it is not commutative is not imo an argument since sum is even more frequently used with a commutative semantics.