I can understand where you are coming from, but you have to realize that it really does come down to an individual's integrity.
Because, if another person sees that a person lacks integrity, then ONE person can determine whether or not compatibility actually exists.
You can tell the integrity of a person, via the words they speak and every action they do. You do not even have to meet this person. You could be overhearing a conversation, become impressed by the person's way of speaking. You could see someone do something that shows obvious integrity trait, and assume whether or not you are compatible with that person, even though you do not know them.
I hoped that helped.