οὐκ ἀπορρητέον οὐδὲ μαλθακιστέον, ὦ ἑταῖρε
what is this? neither forbidding nor slacking? the first is especially vague.
From a glance at the passage, it looks as though they are discussing how to proceed with their investigation - so is he saying they must neither forbid themselves anything (i.e. any topics) nor be lax in their investigation? In other words, they have to be prepared to discuss everything frankly and thoroughly.
IMO, ἀπορρητέον is explained by the earlier reference to his daimon: θεός, ὦ Ἀλκιβιάδη, ὅσπερ σοί με οὐκ εἴα πρὸ τῆσδε τῆς ἡμέρας διαλεχθῆναι
μαλθακιστέον is explained by the ὅτι ἐπιμελείας δεόμεθα
Surely ἀπορητέον is meant. (Minimal manuscript difference between -ρ- and -ρρ-.) Socratic dialogues often end in ἀπορία. They mustn’t let this one do the same. They mustn’t give up, they must hang in there, tough it out (οὐδὲ μαλθακιστέον) and conduct a thoroughgoing joint investigation (σκεπτέον κοινῇ).
I withdraw my suggestion. I think ἀπορρητέον is to be accepted, cf. ἀπειπεῖν in the sense of “give up.”