People aren't buying all those butt plugs for decoration. People fall asleep.
I don't imagine many people sleep with them on purpose, but certaintly possible to pass out with a butt plug in place.
Don't do this too often though! Prolonged dilation (>2 hours) can damage your sphincter and give you incontinence in the long run. Probably not a problem if done rarely, but if it happens regularly it can become a problem
Sadly, there's a lack of formal studies to determine how often is too often. I think "pay attention to your body" is generally good advice. If anything is sore or hurting, it's probably time to take a break. Kegel exercises also help keep the sphincter from weakening over time, useful advice even for people who aren't into butt stuff.
I mean, your hole shouldn't be sore in the morning unless you're sizing up with a new plug. Especially not with a stereotypical conical thin necked black silicone one. I've slept with plugs with a neck diameter of like 1.25" before
It's too much control or trust to place in another person. Even If I didn't have trust issues, It's not something I'd ever be comfortable with. Like you said, to each their own however.
that's fair, though nobody said you had to involve other people, that's just a particularly common and relevant practice. But yes ultimately at the end of the day, it only matters what we care, and don't care for. I just find it interesting knowing why people care about certain things over others.