Monosyllables are by far the largest producers of dialefe in the Divine Comedy, with 2133 occurrences: 1555 listed in Table 2 (1), plus 578 ending in a falling diphthong, the last figure including the one case of io with a diaeresis followed by dialefe.
Example 58 is admittedly marginal to this argument, because of the comma Petrocchi places after si, and in 53 the dialefe after perche could be replaced by a diaeresis on circuito, especially since perche is followed by in.
71 could have a diaeresis on io (which is quite common in the Divine Comedy, as I shall show) instead of the exceptional dialefe, but this would also lose the accented fourth and sixth syllables; so could 76, 79, 80, 83, 92, 98, 99 ('Tal era[??] i|o ...', 'm' andava[??] i|o ...') but at the cost of an unusual accent on the third and the consequent loss of the phrase break, typical of Dante's hendecasyllable, after an accented fourth or sixth.
3 24 49 cosi m' armava[??] io d' ogne ragione My inclination would be to leave the dialefe in example 101, thus preserving the typical phrase-break after an accented sixth, but to replace it with a diaeresis on io in example 100, which in this case would make no difference to the phrase-break (the change is reflected in my statistics).
Of these about half (577) are marked by Petrocchi, and the remainder almost all involve vowel combinations that normally constitute two syllables, and where the diaeresis is therefore traditionally not marked; there are also a very few cases where Petrocchi ought to have marked a diaeresis, in my view, but has not done so, as well as those where I shall argue that his diaeresis ought to be replaced.