I saw a beautiful plant recently and wished I could have a piece of it so that I could start one at home. It was not an unusual plant just a very pretty plant full and well cared for. If everyone pinched off a piece of the plant it would be reduced to a very small plant quickly. I wondered if it would be considered stealing if I did pinch a piece for myself, not that I did it, just wondering to myself. What do you think would you consider that stealing.
I would consider it inappropriate, yes. Instead, why not just ask the owner? Compliment them on how beautiful it is and ask if there's any chance you could buy a 'start' off it. Most people won't even know what this means and even if they do, they're more likely to just tell you you could have one (which wouldn't be stealing). And alternatively, they could at least tell you what kind of plant it was. If you saw the plant in a store, then it would definitely be stealing if you did it and you shouldn't.
Yes, I think it is stealing to pinch part of a plant just like it is stealing to pick a flower from someones garden. The person who has that plant bought it and cared for it. It is not right to do. We recently bought some plants and flowers and probably spent about $70.00 altogether. If someone decided to take some of them without asking I would not be happy.
It would be harmful for the plant if everyone had the same idea as you to pinch off a piece. So you should just give the owner an honest compliment on their plant and ask them nicely if you can have a small cutting to start your own plant. If not, as Jessi said, they can at least tell you what kind of plant it is.