Colon and semi-colon in Donne's prose letters: practice and principle

We cannot know now, and may never know, how Donne punctuated any but one of his English poems.[1] This awkward situation makes it impossible to maintain the twentieth-century editor's drive toward the stability of a fixed and authorial text in the case of Donne's poetry. Perhaps this is not altogether a bad thing: seventeenth-century coterie poetry belonged to manuscript culture, and so was exempt from the requirements of stability introduced by print;[2] we may distort the object of study by making it appear more stable than it in fact was.[3] But modern editorial principles require a standard of judgement in Donne editions. On what grounds can we say that one editor's punctuation is superior to another's?