Membrane staying wrapped around the leaves when seedling pokes up through soil?

Yup - that or the whole seed helmet stays on too long happens to probably 10-20 % of seeds that pop successfully for me. I give em time to try and bust out of it naturally by moisturizing like you said.. but if it doesnt work I will intervene with tweezers.

Yeah it can happen mate, like Hempkid said if you bury them a bit deeper it is supposed to encourage them shedding their shell on the way out the tough moist earth - you did well though, moisten it, let it soften then help it off if it is stuck after a day or two. I do big trays of seedlings for the veg garden and theres always a few that get stuck for some reason or another.