I don’t think you can read Borges without the man himself being within the story. In this particular short story, he places himself there.
A writer to a fellow writer:
The whole affair happened some five years ago. Bioy Casares had dined with me that night and talked to us at length about a great scheme for writing a novel in the first person, using a narrator who 0mitted or corrupted what happened and who ran into various contradictions, so that only a handful of readers, a very small handful, would be able to decipher the horrible or banal reality behind the novel. (p. 17)
So what Borges is doing here is adding the real to the unreality of fiction. First person pov, himself. He’s also hinting at what is to come–a jest, perhaps, or a true lie. And this is what the story itself becomes, a lie about a lie that has been taken as truth. The discovery of this strange planet of Tlon, and in particular, the place known as Uqbar, has a history that is somewhat proven by references in text, previously unknown or perhaps just hidden. He goes into some detail about language, making this knowledge, together with the credibility of the narrator, become something it is not, that is, real.
What he’s telling us too, I think, is that what is written cannot be trusted. For in the history of Uqbar, there is the firm belief that what exists cannot be trusted. Some things exist only temporarily, some just for the few who need to see them. Just before the final closing of the story, is the closing of the research story:
Things duplicate themselves in Tlon. They tend at the same time to efface themselves, to lose their detail when people forget them. The classic example is that of a stone threshold which lasted as long as it was visited by a beggar, and which faded from sight on his death. Occasionally, a few birds, a horse perhaps, have saved the ruins of an amphitheater. (p. 30)
I don’t pretend to quite grasp the full (or perhaps multifaceted) meaning of this short story, but I think that Borges is having fun. Having fun with his free-association way of thinking, and having fun with turning it over to the reader to do some of his own.