When someone often mentions jealousy or others being jealous, isn't that a sure sign of projection?

Projection, my oh my how unlike a robot to use such jargon!!

And that's a good question, no, sometimes people are just plain jealous, and it could be like the sniffles, say you were to have someone jealous over you for a time, and you were never jealous, but then being jealoused at, you become jealous too. A viscous circle it is. Break it by not playing the game any more, be there for others simply for the common good, be pleased with your lot, desire not what was not destined for you.

Low self esteem or no self confidence

Sure seems like it to me, or perhaps a high amount of conceit.
Why would anyone go around even thinking about jealousy.

Yeah don’t be so jelly 😏