Thus the unfacts, did we possess them, are too imprecisely few to warrant our certitude —James Joyce, Finnegans Wake
As a copy-editor I try to abide by the typographic oath: First, do no harm. When you’re making changes to a writer’s text, whatever you do, don’t introduce an error. But at the risk of undermining that solid principle, there is an occasional exception.
Enter James Joyce.
The length and complexity of Ulysses, and the difficulties of its publication, mean that many subtly different versions of the text exist. The first legal edition in the US, which became its standard edition for decades, was based on a pirated copy, for example.
Typographical errors arose inevitably from multiple sources; complicating things further is the fact that some ‘errors’ were deliberate but wrongly ‘corrected’ by printers or editors. And then there were all those rewrites and updates by the author while the thing was being serialised. And afterwards.
So there is no ideal, ‘master’ text; in fact Joyce scholars fight over the best way to decide what this even means.