All things not Allosia or Gabriel belong to JKR.
There was no intended hint in the tenses in Ch. 31 that hasn't been present in the whole construction of this tale, although I'm sorry if you've just caught on. On the plus side, we have a long way to go before we loose anyone, so worry not yet.
Oh and since people have asked, it's "Aloe-see-ah", although the last two syllables tend to get slurred together. Sia is "See-ah".
Word is not saving this right (oi), so please forgive if I can't get the letter into proper italics.
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Sia -
Travel, even in times not such as these, has always unsettled me. I always feel out of place with the world, and just before become preoccupied with the inevitable things that will be left behind, forgotten and lost. There is also a feeling of uncleanness the chaos of travel seems to insist on leaving me with that reminds me too much of what I am, and what I am not.
I am nervous and I wonder for how many weeks you've been waiting for me to admit that. It doesn't trouble me, that you should know it, although I hope we will not find need to speak of it. It is a trivial weakness in a life such as mine, and fundamentally detracts from the power of this particular honor, this particular escape. You do so well at not laughing at me. Would it bother you, I wonder, that I am always internally congratulating you for such forbearance?
We are not so charming as we once were. Not so much in fact, and not even to each other in truth, but to the world, to Hogwarts, and to the friends and family they at least stand in for, we are no longer a story of great interest or hope and that saddens me, although, I do not know the reason why. I feel though, as if I do a poor job of celebrating you and your grace upon my world. I have not the courage to be a Romantic, in most circumstances, and in most cases those excepted circumstances are grim, and are of things you should be, but are too intelligent, to be spared.
I would be a happier man if my flesh never had need to come into contact with any but yours and ours. Even shaking hands unsettles me, forces me into the world in ways I do not wish, reminds me that the man encased in all these layers of fabric as stiff and strange as water, cannot be, as he so wishes, only for you.
Forever at your doorstep,
S.
Snape hummed to himself, as he folded the letter and placed it with the others. He wondered why no one had ever told him that actual requited love, was, in many ways, the greatest hardship anyone could face. It was a labour, as much as a joy, and he wondered absently how anyone managed to succeed at it, especially when the world was populated by those with less intelligence and focus than himself. Maybe the secret was that the world was filled with much less success than he had long imagined.
He sighed then, and ran his eyes around the room, for anything else he might need. In the morning, they would leave for Italy.