People responding reject that, because if you're not being specific, you're not making an argument, you're just here to be an asshole.
Since you've made this point, I've gone ahead and reported that comment.
Suppose their definition for abject poverty is: having an income equal to or below the median income. Yes, they would be right. Is it a problem that they are right?
However, you would also be right in agreeing that having an income equal to or below the median income equates to half the population, so you are wrong to think that only they can be right. Of course, that assumes you have used my definitions for these terms and not your own. It is likely that, once we are updated with your definitions, that you were right all along. What are your definitions for the terms you have used?
That's the beauty of discussion. You don't need to guess. You can ask!
This is absolute nonsense. We use common language to refer to common things in understandable ways in order to communicate with each other. You don't get to just handwave baldly incorrect statements as "well maybe he just has a different personal definition" without basically rendering literally all conversation moot and pointless.
"Yeah, I know he said 2+2 is 5, but you don't know he defines 5" is just as patently silly.
Common doesn't mean ever-present. In practice, it is impossible for everyone to converge on a shared understanding for all terms. There are provably many people in the world who have never even heard the term "abject poverty" before. They cannot possibly understand what the term means to you. Fundamentally, "abject poverty" can only mean in that comment what the author believes it means. That may overlap with your understanding, but it also may not. We can also prove that he is not a mind reader and thus cannot tune it to your understanding. He is limited to his understanding and his understanding alone.
A good faith actor who believes there may be a discrepancy in understanding will seek clarification. That is what a discussion forum is all about. If one does not want to participate in discussion, why be here?