Why do we use commas after "or "?
A loose stretch would wrinkle too easily with successive washes, or might even wrinkle on a damp day.
Since "might even wrinkle on a damp day" is not an independent clause because it has no (stated) subject, why should we use commas to link the two parts?
Commas have several jobs to do in the English language, and one of its most important jobs, according to “reader response theory,” is to prevent confusion for the reader as the eyes travel across the sentence. In one sense the comma is justified here because it signals a series (here a series of clauses, with the subject of the second clause implied.) But more importantly, it signals that the word “or” is not “announcing” a continuation of the first clause by listing prepositional phrases, but rather beginning the next clause. Without the comma, the reader might think the sentence is going to list several prepositional phrases (like this: “with successive washes or with hard rinses or with harsh handling or with sunlight exposure” etc.) The comma lets the reader know that a second clause is starting, not a series of prepositional phrases. The comma prevents “recursive reading” where the reader’s mind must “correct” its first impression and go back to where the communication was unambiguous. In speech, a slight unconscious breath adjustment does the same job.