Hey, Erlend,
Maybe you and that eBay guy have the same seed source! LOL
Seriously though, personally, I don't think it looks too bad, that a little more heat and humidity won't cure. A lot of times seedlings start out like that. Or, what kind of light spectrum does your light system put out? Maybe check with your light fixture supplier to find out if your light a appropriate for bananas. And did you use any kind of growth hormones? Like GBA will do that. A lot of times, plug plants grow similarly in the first 3 to 4 months, or more, because of the hormones the labs use. I have Dwarf Orinocos from TC that look like that now, only bigger and taller, since it's been 14 months since I got them from Agri-Starts.
The Dwarf Nino was also the same, until last July after I transplanted them in bigger pots. Last July, it would be the second year I've had them from A-S. Before that, the leaves had pointed tips. The leaves that developed since then are now rounder at the tip.
Back in 10/27/2006, Barna posted some photos of M.Nagensium, including what looks like a seedling. (
Musa nagensium seeds for reference ) And yours looks something awful close, except for size. The coloration is even somewhat similar.