Originally Posted by
RandomBaritone
...a friend told us we may face some uncomfortable questions from the tour guide (?!) and even from Russian passport control if we, for example, wear our wedding rings.
Does your friend know this from personal experience?
In any case, the least person to worry about is the tour guide! They are there to make business, not to judge anybody.
In St. Petersburg, you will be the guys with the tour group visiting the typical tourist sites. There is minimal chance you will have any problems.
Of course, this is assuming you won't be wearing Rainbow T-Shirts, carrying rainbow flags or chanting "We are Queer, we are Here".
Your wedding ring will go unnoticed.
I wouldn't worry.