Well, I had those conversations a long time ago, but we can describe some general patterns.
We can smuggle in presumptions through the use of attributive adjectives. In the above comment (which you might have noticed I wrote in E-Prime) I mentioned smuggling in "covert presumptions" of "essential attributes". If I had instead written that in assembly language as follows:
I smuggled in presumptions of attributes.
The presumptions were covert.
The attributes were essential.
it would clearly violate E-Prime. And that forces you to ask: does he intend "covert" to represent an essential attribute of those presumptions, or merely a temporary or circumstantial state relative to a particular temporal context? Did he intend "essential" to limit the subjects of discourse to only certain attributes (the essential ones rather than the accidental ones), and within what scope do those attributes have this purported essentiality? Universally, in every possible world, or only within the confines of a particular discourse?
In these particular cases, though, I smuggled in no such presumptions! Both adjectives merely delimit the topic of discourse, to clarify that it does not pertain to overt presumptions or to presumptions of accidental attributes. (As I understand it, Korzybski objects to the "is of predication" not because no predicates exist objectively, but because he doubts the essentiality of any predicates.)
But you can use precisely the same structure to much more nefarious rhetorical ends. Consider, "Chávez kicked the squalid capitalists out of the country." Well, he kicked out all the capitalists! We've smuggled in a covert presumption of essentiality, implying that capitalism entails squalidity. And E-Prime's prohibition on the copula did not protect us at all. If anything, we lose much rhetorical force if we have to explicitly assert their squalidity, using an explicit statement that invites contradiction:
The capitalists are squalid.
We find another weak point at alternative linking verbs. It clearly violates E-Prime to say, "Your mother's face is uglier than a hand grenade," and rightly so, because it projects the speaker's subjective perceptions out onto the world. Korzybski (or Bourland) would prefer that we say, for example, "Your mother's face looks uglier to me than a hand grenade," or possibly, "I see your mother's face as uglier than a hand grenade," thus relativizing the attribute to a single speaker's perception. (He advocated clarity of thought, not civility.)
But we can cheat in a variety of ways that still smuggle in that judgment of essentiality!
Your mother's face turned uglier than a hand grenade.
We can argue this one. Maybe tomorrow, or after her plastic surgery, it will turn pretty again, rather than having ugliness as an essential attribute.
Your mother's face became uglier than a hand grenade.
This goes a little bit further down the line; "became" presupposes a sort of transformation of essence rather than a mere change of state. And English has a variety of verbs that we can use like that. For example, "find", as in "Alsup found Dahmer guilty." Although in that case "find" asserts a state (presumably Dahmer became guilty at some specific time in the past), we can also use it for essential attributes:
I find your mother's face uglier than a hand grenade.
Or lie, more or less, about the agent or speaker:
Your mother's face finds itself uglier than a hand grenade.
And of course we can retreat to attributive adjectives again:
Your mother has a face uglier than a hand grenade.
Your mother comes with an uglier face than a hand grenade.
Or we can simply omit the prepositional phrase from the statement of subjective perception, thus completely erasing the real agent:
Your mother's face looks uglier [...] than a hand grenade.
Korzybski didn't care about the passive voice much, though; E-Prime makes it more difficult but, mostly, not intentionally. As an exception, erasing the agent through the passive voice can misrepresent the speaker's subjective perception as objective:
Your mother's face is found uglier than a hand grenade.
But that still works if we use any of the alternative, E-Prime-permitted passive-voice auxiliary verbs:
Your mother's face gets found uglier than a hand grenade.
As Bourland said, I have "transform[ed] [my] opinions magically into god-like pronouncements on the nature of things".
As another example, notice all the times I've used "as" here. Many of these times smuggle in a covert assertion of essential attributes or even of identity!
But I found it very interesting to notice these things when E-Prime forced me to rethink how I would say them with the copula. It seems like just the kind of mental exercise to heighten my attention to implicit assumptions of identity and essentiality that Korzybski intended.
I wrote the above in E-Prime, by the way. Just for fun.