I’m trying to understand why the participle is in the accusative here. Can we take the συγχωρεῖν as an epexegetical infinitive (modifying ἐξαρκοῦντα) which then governs the subject-accusative participle? Or does ἦ γὰρ somehow initiate an indirect clause?
Yes, I see the accusative infinitive construction. But what governs this accusative infinitive construction? I see no indirect speech-- no verbs of thinking, seeing, etc.
In your example einai is the implied subject, “to be foolish is painful”. But I don’t see how the infinitive in the Hippolytus passage can stand as the subject of the sentence.
We could say “Is this your idea of fairness, first to wound me and then to …”. I wouldn’t worry about whether ταυτα or the infinitive phrase is technically the subject. What’s more important is that the ταυτα comes first and the rhetoric demands that it’s taken first. If you want to call the infinitive epexegetic, be my guest, likewise if you want to call it the subject (you can’t call it both), but do respect the sequence of the two verses.
The ἦ γάρ effectively conveys her indignation. I expect Denniston has something on this. I translate it as “?!”