Would you expect to see a folded mountain range at a mid-ocean ridge?

No, since folded mountains only occur when two continental plates collide; I think the reason for this is that only continental plates have the mass to push upward into folded mountains. Ocean plates, since they are relatively thin, will not fold upward, I think.

In any case, the mid-ocean ridges are all formed by rifting, when two plates are drifting apart. In this case, folded ridges cannot form; instead, the ridge is formed by new lava pushing up and cooling into igneous rock at the edges of the plates.