[kergonath]

The point the parent was making is that it is not incorrect or misleading, just ambiguous. And even then, it’s ambiguous only if you leave out the second clause.

“I could have a banana” has two perfectly correct meanings: it is possible for me to have a banana right now depending on some factor (conditional), or I had the possibility to have a banana in the past (preterite).

A preterite in the second clause eliminates the possibility of a present conditional in the first one.

[PebblesRox]

Don't you need to add another verb for “I could have a banana” to work as past tense?

E.g. "I could have eaten" or "I could have had"

Edit: Oh wait, now I see it. Something like "I knew I could have a banana if I got hungry."