Though I'm a bit obsessive about original spellings etc. myself, I'll agree that modernization of spelling and punctuation is absolutely legitimate. Editors of classic texts have been doing it for ages. The older the text, the more the strangeness of spelling and punctuation can distract from the text itself, so I can understand every reader who prefers modernized spellings. I still remember vividly the time in 8th or 9th grade when we read one of Goethe's plays (I'm German) in the original spelling -- it took quite a while before we stopped making jokes about some of the -- to us -- weirdest spellings; I am sure we would have arrived at the content of the play sooner if we'd read it in modernized spelling.
And "original" spelling has its pitfalls too. Sometimes editors have felt entitled to make major changes, especially if they thought the writer lacked education (John Clare is a famous example). Or in German there's Heine, who for instance liked to spell his /ai/ sounds "ey", which was already becoming old-fashioned in his day, so many magazine editors who published his poetry modernized it to "ei." Some modern editors, aiming to be true to the author's intention, changed it back to "ey," even though some poems were never printed that way. Of course that is all well and good in a heavily footnoted critical edition, but how would you decide if you wanted to prepare a reading edition?
Or, in the case of John Clare, on the one hand it is known that he had bitter arguments with his editor about some changes, but on the other hand nobody can say for sure if he really wanted to see all his spelling errors in print.
Hence, there is no Golden Rule here, except: do what you like, best indicate your editing policy, and find happy readers.
