A detector should be expected to misread polished historical prose sometimes, especially when the passage is formal, repetitive, and highly edited. That does not make the test pointless, but it does mean the label needs to stay narrow.
The first step is to identify what text is actually under review. In this case, the Lincoln passage is quoted material. The student is not claiming to have written it. Running that quotation through a detector tells you nothing useful about whether the student composed the rest of the discussion post. For the quotation, the relevant checks are much simpler:
- Does the passage match a reliable transcription?
- Is it attributed to the correct speech?
- Did the student quote and cite it according to the assignment rules?
- Does the student’s own commentary show that they understand why they used it?
The next step is to separate authorship from processing. “AI-generated” gets used as if it describes a single event, but several very different things can produce the same submitted text. A person might generate a whole response, ask for grammar edits, use autocomplete, modernize punctuation, clean up an OCR scan, or simply paste a historical quotation. Those cases should not be treated as equivalent. A detector cannot reconstruct that history from the final wording.
Formatting sensitivity makes this even messier. If restoring line breaks changes the result, then the classifier is responding to the representation of the passage, not uncovering a stable fact about its origin. Humans consider both versions the same speech. The system may treat them as different sequences with different patterns. That is useful information about the detector, not about Lincoln.
I would translate the result into plain language: “The detector found this version similar to text in its AI category.” That is about as far as it can go. It cannot tell you whether a student typed, pasted, dictated, edited, or generated the passage. It certainly cannot override known provenance.
For an instructor, the better evidence is usually found around the text rather than inside a probability score. Compare the student’s explanation with the assigned reading, check whether the quotation exists at the cited location, and ask a specific follow-up about the argument. If the student can explain the connection and the citation is accurate, the detector’s opinion about a nineteenth-century speech is mostly a distraction.
So I would use the Lincoln example as a boundary test. It shows that “AI-generated” is often shorthand for “classified as resembling generated text.” Those are very different claims, and only the second one is supported by the tool.