Sir Richard C. Jebb, Commentary on Sophocles: Oedipus at Colonus

καὶ εἰ ἐπερρώσθη (impersonal) even if courage has come to them δεινὰ λέγειν to say dread things τῆς σῆς ἀγωγῆς about your removal (for the gen. see on 355: for “τῆς σῆς” as=an objective “σου”, on 332). The normal phrase would be “κεῖνοι ἐπερρώσθησαν”, and the use of the impersonal form here is bolder than in the ordinary passive examples (usu. with perf.) such as “ἱκανὰ τοῖς...πολεμίοις εὐτύχηται” (Thuc. 7.77). Possibly the common impers. use “ἐπῆλθέ μοι λέγειν” (“"it occurred to me to say"”) may have helped to suggest the impers. “ἐπερρώσθη”.

λέγειν. An inf., which here depends on the notion “ἐτόλμησαν”, does not elsewhere occur with “ἐπιρρώννυσθαι”, but stands with the simple pf. “ἔρρωμαι” as=“"to be bent on doing"” ( Lys. or. 13. 31 “ἔρρωτο...κακόν τι” “ἐργάζεσθαι”). Whitelaw: “"though terrible things were emboldened to the utterance,"”—comparing 658 “ἀπειλαὶ...κατηπείλησαν”. But, if the “δεινά” are personified, do we not then want a stronger word than “λέγειν”?

We cannot read “κεῖνος”, since the pl. is needed. The best solution would be “κείνοις δέ, κεἴ τις”, from which “ἴσως κεἰ” might have come through a transposition. But the sarcastic

ἴσως is fitting: cp. Ai. 962 “ἴσως τοι, κεἰ βλέποντα μὴ ᾿πόθουν ι θανόντ᾽ ἂν οἰμώξειαν.”

κεἰ here where “εἰ καὶ” would be natural (as granting the fact); whereas in 306 the “κεἰ” is normal: see O. T. Append. Note 8, p. 296.