Aaaaah, don't worry, your deck is untouched and I wouldn't trim it! I'm only a lowly tarot user, not even a serious collector, but your question is a good one for a half-baked collector like me.
I wouldn't trim an independent deck. And you know I trim freely, I have proofs for that. But when I know that an independent artist produced a deck, then I relate to it differently than when I know it's a mass produced object.
Let me explain why.
First of all, obviously a deck like yours is more expensive, more rare and if I trim it, I spoil it as "investment" should I ever wish to part with it (which I don't). A Lo Scarabeo or Urania Königsfurt deck can be replaced if I want to own an untrimmed version again.
But it's more than that. When I buy a deck like the Fey or Lo Scarabeo or Universal, I know that this is a deck that was made by a lot of people. Author A wrote the concept, the publishing house looked for an artist, the two worked together (the Fey Tarot book shows it's a fascinating process), and the result is the work of many people. A publishing house takes the deck from the artist's hands, decides about fonts, size, proportion, frames etc. They're most often not part of the artist's vision. (That's at least what I understood from reading accounts of people who published decks). The publisher has a whole team of people.
I'm certain that the people who put the atrocious border on the Lo Scarabeo were neither the author nor the artist. It's a totally un-connected piece of blandness. I relate to it like to a committee decision.
I can go against the committee because as buyer and user, I feel part of it. I will not go against the vision of an artist who dreamed this deck from A to Z and had sleepless nights over every decision.
I'm sure that Kat Black had a say in the borders around her decks, and I don't trim them. I wouldn't dream of trimming decks where I feel the border bears the handwriting of the artist, or the artist was at least consulted, or his/her vision played a role. I didn't trim the Shadowscapes, Anna K. or any Robert Place deck. The borders look good, they belong there.
But the Haindl? Who decided to pair his earthy art with sickly grey-greenish huge borders?
So it's not disrespect of the artist but a wish to see the artist's work without irritating additons that lead me to trim.
In the case of the Thoth - I don't know whether Frieda Harris sanctioned the borders or Crowley. And I don't really care to be honest. If they wanted the information printed on the card, well, I have the information in my head. And the art looks glorious when the cards touch each other. I showed an example some days ago in the Thoth thread.
And the Lo Scarabeo, the best example imho for the difference a trim can make:
Untrimmed, trimmed, rounded corners.
The Night Sun BEGGED for a trim. The white borders neutralized the harshness of the images.
Obviously, it needed a black edge, too.
This looks also much better.
And the Haindl.
But no, don't worry, I won't do any harm to your deck! It sleeps right now in a cozy bag with its friends, to be taken out regularly.