My instinct is that if the community decides it is "just kind of weird", then it is a useful shorthand that we wouldn't lose anything from standardizing on.
It is *very* weird, and therefore not a "useful shorthand."
In JavaScript, "delete" means "remove this property / interface from this JavaScript object." I can't think of any context in which it means anything else.
For example, "delete node.parentNode" attempts to remove the "parentNode" property from "node". It does not remove "parentNode" from the document or anything like that.
"delete window" attempts to remove the "window" property from the global object. It does not close the window or anything like that.
In other words, you can be certain that "delete" is a simple operation with a consistent side-effect.
As a JavaScript programmer, I would find it very difficult to reason about objects that might or might not change the behavior of the "delete" operator. One reason i would find it very difficult is that operator overloading does not exist in JavaScript at all, so to understand this one API, I would need to understand a vast corpus of programming language goobery that is not at all covered in any JavaScript manual. Another reason I would find it very difficult is that the overloaded meaning of "delete" here ("remove persistent storage from disk") is far afield from the original meaning ("remove interface from temporary object in memory"). To give you an analogy, even in C++, where you're allowed to overload operator delete, if you overloaded operator delete to mean "do not free this object's memory, but do delete the file it references from the file system", well, let's just say that your patch would not pass code review with any of your four reviewers :).
I am not sure if any JS decoration or collection libraries depend on the canonical behavior of operator delete, but if they do, I would hate for them all to have to ship with the asterisk, "BEWARE: do NOT use this decoration / collection library with that one weird DOM object that interprets 'delete' to mean 'remove important data from the user's disk'". Oy!
Geoff