It's trying very hard to sound smart. But "...something with a non-empty include set that contains only x..." is the same as "...something that includes x and nothing else..."

There's this quote from a famous (in strictly relative terms) judge on the German Supreme Court: A good lawyer or judge will, according to him, "think like a philosopher and talk like a peasant!".

Of the three other possibilities, two are still fine. But trying too hard is a mortal sin.

This sort of comment is often similar to a North American hearing a British person speaking in their natural accent, and going "why are you trying so hard to sound fancy, dude?"

In fact, your own quote speaks to this: when you're thinking like a philosopher, it's easy to also speak like a philosopher; what takes effort is to speak like a peasant (and we've all had similar experiences with technical jargon in our own field, and having to translate that to a layperson). You can certainly accuse them of not having tried hard to translate it to simpler language, but it's an unwarranted accusation to say they're "trying very hard to sound smart" when they're using language that is similar to their own thought processes, and hence is probably easier to write in.

Reminds me of a scene in "I, Robot" (the movie):

Del Spooner: So, Dr. Calvin, what exactly do you do around here?

Dr. Susan Calvin: My general fields are advanced robotics and psychiatry. Although, I specialize in hardware-to-wetware interfaces in an effort to advance U.S.R.'s robotic anthropomorphization program.

Del Spooner: So, what exactly do you do around here?

Dr. Susan Calvin: I make the robots seem more human.

Del Spooner: Now wasn't that easier to say?

Dr. Susan Calvin: Not really. No.

I agree, communicating to big demographics with individuals of diverse backgrounds is a skill that a lot of people either don’t have (and choose not to cultivate) or don’t even know is a learnable skill. People on the internet take this for granted and just think all the great articles they read on the internet could have been written by anybody (which a lot of the times is untrue)

You're presuming that every phrase was worded _just so_. This could very well have been from the author refactoring their sentence and not simplifying everything. They probably were thinking in these terms (the author is a PL guy from MSR who's pretty heavy into a lot of the formalism) and this sounds like a not-perfectly-polished formal thought.

It's technical, and sometimes technical writing isn't written perfectly. That doesn't mean it's due to willful obtusity, or trying to sound smart.

Perhaps there is one description for existing programmers (who would appreciate the comparison to variable binding) and one that doesn’t (who could care less about that)?

Hi Sean, yes - that is the case. I've regrouped the documentation to make this clear. Happy to have any suggestions for improvements. This is just a starting point.

Hey Tom. Ya, I would guess that making some kind of material to get end users to understand this would be more challenging than getting us programmers to :) (and probably half the fun of the project).