I wonder if all those abnormalities of Allens innocence that we have witnessed are not due to him being one of Heart's halves, but on the contrary are a result of his Noahness. Given that Innocence was said to be Noahs weakness it may sound strange, but considering the fact that innocence's greatest weakness are Noah too (as they can destroy it), it may not be so anymore. Givien this two facts, a good question rises - how were this two powers (of a Noah and Innocence) were able to coexist within Allen not causing him any trouble. It may be said that this was due to Noah's side sleeping (being in inactive state) all this time and being awakened only in Ark, when a time for Musitian had come. But then again - why no conflict has arised after they awakened?
I assume that it is because yje two opposite powers have managed to merge somehow. Not recently, of course, but long ago. In this case it may be them who are responsible for Allen's innocence strange behaviour - back then, when Tiky destroyed it, he couldn't do it completely because he had no ability to destroy Noah's power, that had entered Allens innocence, and because of that fenomenon they have managed to survive. It also may be Noah's side responsibility for that Earl-like sword appearance, but since we do not know if it could be created without Noah's power or not we can't say so with confidence.