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Context makes all the difference.
There are three potential potential solutions here:
Any of those choices are arguably correct, depending on how one regards the image. The easiest one to refute is the first option. This caption may be obscure after a century and a half, but to me it looks like an explanation of the original artist's choice to juxtapose the president in coat and tails against a reference to his humble origins. Of all the people who became United States presidents, Lincoln started out life lower on the socioeconomic ladder than any other. Hence the references to manual labor, which seem to result in a compliment to Lincoln's hard work and perseverence bringing the country back together at the end of the Civil War. The artist's caption helps explain that; I decided to leave it in.
So if we keep those darn borders, do we fix them? Do we rotate individual lines and make them correct? It can be argued that is not artistic intent, that it's distracting, and it ought to be fixed. It can also be argued that slight variances from mechanical perfection are characteristic of the period, therefore historical, and ought to be kept. When they performed a digital restoration on the 1939 film The Wizard of Oz they erased the wires that had lifted the flying monkeys. I'm a Wiki Witch; I prefer vintage monkeys in their original technical imperfection even if it takes me out of the story just a little bit.
So I selected a compromise rotation and cropped a little extra space outside the border lines to minimize attention to that flaw. The closer an uneven border comes to the edge of the digital image, the more apparent any deviation is.Ragesoss complained about the final choice here and, to be candid, it wasn't my first crop either. Originally I had kept the side borders and I'd left leeway outside them because they were a few hundredths of a degree off from true. But the area outside the border on the original has uneven tone, especially the blown whites at lower left. And although the file was big enough to work with it wasn't ideal. I could have filled in the problem tolerably but the technical limitations of the file didn't make it worth the effort. Overall, for an image that most viewers will see in thumbnail, a good rule is to crop in as close as feasible. These kinds of decisions are often tradeoffs, and arguable either way.
If you haven't read Titus Andronicus (and Wikipedia's excellent restorationist Shoemaker's Holiday hadn't), there's not much need to regret that particular gap in an education. Even the best of them can turn out one real dud. The only analogy that came to mind was a stretch. If Shakespeare is the Steven Spielberg of the stage, then Titus Andronicus is Shakespeare's Howard the Duck. Shortly after getting that explanation Shoemaker read the plot summary. It wasn't the cannibalism that bothered Shoe quite so much as...eh, well...find out for yourself if you dare.
Shakespeare scholar Harold Bloom has claimed that the play cannot be taken seriously and that the best imaginable production would be one directed by Mel Brooks.Shoemaker, though, was interested in a detail. And that detail is worth attention as an example of digital image management.