Not sure what went wrong. I bought a fey chainmail in the AH, that was already disjuncted. It had a blue slot. Said it was ML 2.
Used an ML5 shard, added constitution and healing amp, and ended up with a ML10 item. Not sure at what stage it became ML10, didn't notice until I was finished.
To experiment, I bought a disjuncted splintmail from the AH, not fey, but did have a blue slot. It also said it was ML2. Also used ML5 shard, and constitution. Didn't have mats for healing amp, so I added false life instead. This item is ML5.
Comparing them, they are very similar, just fey chainmail has I think +2 ac compared to the splintmail (and of course healing amp vs. false life). The stats on the ML10 chainmail are very bad for an ML10 item, it really looks like an ML5 item.
Did I miss something, or does this seem like a bug?