English Translation
I didn’t know you couldn’t sing.
(I didn’t know you couldn’t sing) I have come across this type of sentence where the second verb (in this case, riuscivi) is in the past subjunctive rather than the imperfect. (Non avevo idea che non sapessi nuotare.) There seems to be an exception when the second half is factual rather than supposition, but is it more narrowly confined to the use of the verb sapere in the first half?