In the 2-volume John P. Jewett edition, thin spaces precede the apostrophe in contractions. So one has “I[thinsp]’ll” or “he[thinsp]’d.” Negative contractions have the thin space before the n, so “could[thinsp]n’t” “should[thinsp]n’t etc.
But the edition has no space before an s to indicate possession. So (in chapter 1), Haley does not observe “Murray’s Grammar,” and Eliza’s son Harry takes up his “master’s stick.” (no space). In chapter 2, Mr. Harris claims to own George under the logic of slavery. He says “The man[thinsp]’s mine” (1:31). But he does not use possession. Mr. Harris uses a contraction for “man is mine.” When the thin space is present in the Jewett 2-volume edition, that form is distinguishable, by the presence of a thin space, from all possessive forms of man’s, such as when Chloe gets her “ole man’s supper” (1:38-39). When the text is modernized and that thin space is removed, the distinction between a possessive form and a contraction disappears.
In the modernized editions that I’ve looked at (Douglas, Ammons, Yellin), this distinction, which was present in the nineteenth century first book edition, has gone the way of the i/j and u/v distinction in Renaissance print. Is mis-spacing a form of a mis-spelling?