Per an online dictionary I just consulted, a trope is
any literary or rhetorical device, as metaphor, metonymy, synecdoche, and irony, that consists in the use of words in other than their literal sense.
This sounds like the definition that Rae Bryant gives in the essay, but does not seem as if she then discusses literary or rhetorical devices.
As Delany pointed out years ago, it's hard to use words "in other than their literal sense" in SF, since SF describes a new reality, which needs -- usually -- to be described literally.
Some rhetorical forms are so well assimilated into the language that everyone uses them, and no one sees them as figures of speech any more. You can see this in spelling: "tow the line," "reign in." The underlying image has been lost.
These can used in science fiction.
I did not mean to post this. It was still a draft. But I did post it, and it got one comment, so I guess I am stuck with it.
Josh points out that trope can mean convention, which is not a cliche. I know the word from SF con panels, and most of the people using the word are not trained in literary criticism. So what they mean -- or maybe what I heard -- is more like gimmick than convention.
But it does seem to me that Rae Bryant is using the word to mean convention, which solves part of the problem for me in understanding the essay.
It seems obvious that SF is full of conventions of plot and character and device (consider FTL), but is not full of metaphoric language.
Speaking from 35+ years of experience, I will strongly recommend that SF writers stay away from irony. I have used it consistently, and it has consistently confused editors and readers. In SF it's a good rule to say what you mean and mean what you say.