In the really excellent edition of Antigone by Mark Griffith, we come across the passage above in the third choral song, and are immediately struck by the rather strange dative plural Θρῄσσησιν, or Θρήισσησιν if you prefer. Why not Θρήισσηισιν? Is this a new form, or was somebody suffering from iota fatigue?
That seems to be a reference to the Oxford Classical Text Sophocles, where the Preface says, and in English, strangely enough:In matters of orthography we have paid some attention to the evidence provided by epigraphical discoveries, even though one cannot be sure that poets followed exactly the same rules as officials responsible for drafting public decrees. [p xiii]
It seems reasonable that if you were having lots of stuff engraved in stone you would naturally try to leave out iotas or indeed anything else.
Apart from that, Griffith seems to be indicating by modest silence that he prepared his own edition of the text, but it looks as though he may have been starting from the OCT rather than actual manuscripts.