I just recalled another example of a deeply religious person whom I knew as a child in the former USSR. It was my great aunt, my maternal grandmother's sister Kateryna (I called her "aunt Katya"). She was a medical doctor, a surgeon by training, and a lifelong Army officer. In the 1930-s, she married a man, called Mikhail, who was, like herself, an officer of the Army medical service, and who during the WWII became a general. After the war, they settled in Moscow (Mikhail was a Russian and a Moscow native). He suddenly died of a stroke in 1948 - quite amazing, not having even a scratch from the war, even though he was on the front line all the time. He was not yet even 50.
Aunt Katya was devastated. She never re-married, retired from the Army and lived very solitary life in her apartment in the northwestern outskirts of Moscow. All of her life became centered on two things: her sister (my grandma in Kyiv) and her sister's family, including me, and the Orthodox Church.
I did not realize it at that time (when I was little), but later I learned from my relatives that my aunt Katya actually attended a small Orthodox parish every week, often several times a week; she went to Holy Confession, partook in the Eucharist, had icons in her apartment, etc.
When she was visiting my grandma, she never talked about anything religious, but she was, indeed, VERY different from all my other relatives. She was extremely quiet and soft-natured; it was just impossible for me to even imagine how my aunt Katya could raise her voice or say anything crude, any word that could hurt people. She was also extremely, unusually modest in the way she dressed, and in her manners at the family dinner table: she ate so little, always asking to give her a smaller piece, or to cut some piece for her into two halves and give her just one half. My grandparents and my grandma's brother (aunt Katya's younger brother, also a military doctor) always laughed and poked fun at her, calling her "Katya-polovinka" ("Katya the Half").
And, most importantly, she was so amazingly kind to anyone and to me. It was always a very special time for me when aunt Katya was in Kyiv, because she would take me for long walks in the city parks, telling me most exciting stories about the war, about how Mikhail and her served in the Army from the first day of the German invasion in the USSR (June 22, 1941) till the capitulation of Germany on May 8, 1945, which they learned about when they were in Vienna.
Having had such a hard, tumultous, military, combat background, my aunt Katya, again, was an amazingly quiet, soft-natured and kind person. I believe she was a true saint. My mom still says that aunt Katya's eyes and her whole face had some kind of a very unusual, special glow, a shining.
Again, I am sure that the Soviet authorities knew about my aunt Katya's religious life. But there was probably no reaction on their part, no persecution, even in the 1950-s and 60-s (Stalin's and Khrushchev's time), because she became a very private person, a retiree, and she kept her religious life very much to herself.