How would a bruise just start on the stem like that? I'm just curious. When I got the plant it was entirely green. About it spreading, it does only stay on the stem, but the oldest smallest leaves do peel away from the plant where it gets black.
I am very glad to hear you say that black staining is normal. I admit, I have been searching out lots of photos of banana plants, hoping to see something similar. I guess I will let it be. Then I assume I don't need to isolate it from other plants?