When I was about 10 years old, somebody was getting "sustained" and got "opposed" by some members in the ward. The Bishop at the time took them out to foyer. That's all I remember.

Once in my ward some inactive members came to church once just because they knew that their mortal enemy was being put in as bishop and they wanted to oppose him. It was rather awkward and the person at the pulpit said, "we'll talk after." I remember asking my parents what they would do and they said they would just ask them why they opposed, and if it was because of some terrible sin that only they knew about they would not allow him to be a bishop.

Wouldn't God know not to call him if he had sinned terribly?

This is how I saw it handled in the 60s and 70s.

Sometimes the person served, sometimes they didn't.

You mark yourself as an apostate.

who was appointed to a fairly important position (I don't recall now what it was.) This guy was such a total asshole that I wouldn't have nominated him to be the local dogcatcher. I knew that he and DH had had some fairly heated words on various topics in EQ meetings.

When the usual sustaining vote was requested, DH sat perfectly still with his hands in his lap. Of course I followed his lead, as I had no use for the jerk either. The SP or whoever was directing the sustaining glared at DH very pointedly, and DH looked back, very calmly.

After Sacrament meeting, the bishop caught up with DH and said, "I noticed that you did not sustain Brother So-and-So." He waited for some kind of explanation. DH just said, "That's right. I didn't. Please excuse us, we don't want to be late for Sunday School." He turned on his heel and walked away. Of course, I did, too, thrilled with this sign of open rebellion.

We never heard any more about it.

What if when you hold your arm to the square to sustain someone, your square is not very square? Does that mean you oppose the person?

I did it once, and they looked at me and ignored it. Once at stake conference about a dozen people opposed a move the stake made, but they didn't even take their names. Once a former branch president drove miles to oppose making a guy an elder. He was interviewed by the stake people, told he was wrong, and just months later the new elder, after taking his wife through the temple, murdered his wife. Looking for inspiration and dialogue? Not in Mormonism.