The OP's thread is so broadly posed that for the sake of logic, it is meaningless. However, members immediately interpreted it to be about issues, especially their own problematic personal often emotional involved relationships, that can be misinterpreted that are a very minor subset. An issue on this board is numbers of those that seem to like starting threads, don't bother considering how others may interpret whatever simplicity differently than what is going on in their own mind. Note I'm not picking on just the OP but rather most of those that create threads.
Two major reasons people often don't understand each other is because either the person presenting whatever doesn't adequately, clearly explain and the second is the other person is listening poorly that may or may not be their fault. For example, if someone starts talking to you while you are wearing earbuds listening to music, don't expect them to understand what you are saying. If one is helping someone in their car stopped at an intersection light with directions to the nearest gas station, don't expect them to be able to understand when one starts rambling away with dozens of street changes to get wherever.
Years ago, I worked at tech companies with lots of supposedly very intelligent and educated people, where HR tried to improve these interpersonal communication issues by holding in-house classes. It always surprised me how many such high IQ people had such poor interpersonal communication skills that of course is even worse in the blue collar working world. Just consider how easily manipulated so many are on social media and news media.
When I'm at a retail checkout counter and relate, "Yes I have a bag" or here is a Twenty ($20), the clerks always understand.
When I send a smartphone message to one of my relatives that I'm going on a short road trip so won't be around tomorrow, they perfectly understand and won't be phoning me as though I was.
When at my job and told an electronic tech that that reason the PCB still doesn't work after they replaced an IC, was because they put the wrong part in, they totally instantly understood.
When on this web community board, when I relate that I'm 5 foot 6 inches, people always understand what that means.
When on this web community board, when I talk about complex neuroscience, I expect few members will understand more than little bits.
When I tell an 8 year old kid that 2 plus 3 equals 5, or that A is the beginning of the English alphabet, almost all comprendo.
There are a zillion other examples one might add.
So what is the OP much more narrowly asking?