I bought some red onion sets yesterday, having just finished making a raised bed for them.
A few had started to sprout but some of the others had mould on them. It didnt look like the whole onion was mouldy, just the outside layer.
I have planted them (all 100, my back is killing!) but was this a waste of time? All the others in the shop looked the same.
I would think the most important thing is that the bulb is firm.If it is mouldy and soft I'm sure you have wasted your time but if firm ,out in the fresh air they should be fine . Good luck anyway!
A litle bit of mould shouldn't matter - I've planted them like that and they're alright. As long as they weren't completely rotten you should get some reward for your efforts. Give them a good feed of seaweed to get them started and then another top dressing of fish, blood and bone in March.