I was a Jeffersonian Theist (aka, a flavor of Deism) for decades, all the while attending Methodist version of Christianity.
I did not hide, per say, that I did not believe Jesus was even a little divine (and back then, I still thought he was a historical, these days, not so much).
I had tossed out Hell Theology and all the trappings that went with-- yet it seldom came up, and indeed, I was often surprised to run into a fellow Methodist, who not only believed in hell, but in demons, devils, evil spirits and what-not. Sometimes, it literally astonished me-- but I learned how to mask my surprise, and to just nod and "mmm-hmm" to get along.
So I suppose I was a Closet Deist for decades-- does that count?
I only kicked the last trappings of Theism, when I recognized that I did not have any faith in any god(s)-- not even nebulously ill-defined ones. I used to love the movies by the late George Burns,
Oh, God! because they were so very close to what I thought. Now, they are simply amusing, and a little cute.
It was kind of surprising, really, to realize a couple of years after the last dregs of faith had left me, that I was ....
an atheist. (involuntary shudder) I was laboring under many Straw Man versions of what that actually was-- not the least Ayn Rand-ism (as ugly an example of Human Selfishness and Hypocrisy as you'll ever see).
So, in a way, for several years (around 2005) I was in the closet about being atheist. When asked, during those days, I'd reply "unbeliever" or "ex-believer" or (in a joke-tribute to QM) I'd say I had "Quantum-Faith", a kind of nod to Agnosticism.
These days? I only bring it up, if the subject comes up in conversation, in meat space. On the Intertubes, I'm pretty out-and-loud about atheism. But in meat space? I simply ignore that which some would find offensive-- I refuse to give them permission to offend me-- someone says, "God Bless" or "Have a Blessed Day"? I reply with either a nod-and-smile, or a thanks or similar-- depends on the situation. Why let them get to me, and spoil their day? Within seconds, I'm well away, and have forgotten the interaction, and they are on to the next customer, not realizing that their blind assumption that everyone is as theistic as they, isn't even a majority position anymore...
Same for family pray-time-- which is frequent-- I now stand (or sit) there quietly, but refuse to bow my head, or even close my eyes. I may look down a wee bit, but I decided that to set an example to the young'uns in my extended family: Not everyone believes in the Woo. They may find a Kindred Spirit (or they may laugh-- or even hear "he's of the devil" behind my back-- don't care anymore about such silliness).
Some would say, "But you gotta RESPECT their Traditions!"
No. You don't-- I'm not disruptive. I'm not humming, or going ahead and eating, nor tossing fake blood on fur, here-- I'm simply waiting silently until they Cast Their Magic Ritual over the food. But it's a silly notion: As if the Ultimate Creator has Got It All Wrong, and Needs Correcting or something. THAT is how I see praying. Or worse-- "thanking" a Magical Ghost, while 100% ignoring the human hands that made it all happen: From the farmers who planted the crops, to the migrant immigrants who harvested it (at too low wages) to the truckers who hauled it all the way to here, to the hard working grocers who put it all out in an appealing display, to the family members who prepared it all... None of those people get a mention. But Magic Sky Fairy gets credit? I could say these things and more-- but I remain silent and amused.
Magic Rituals are like that-- reminds me of Snow White, or Cinderella or even Star Wars.
May The Farce Be With You
... and Also With You.