#20 indicates "breaking rapport with body language" which I interpreted as looking away, shifty, crossing arms, standing at angle, fidgeting, and other behaviours neurotypicals may construe or indicate as not paying attention. In other bullet points, I think it broadly means non-paralelizing or non-matching behaviour - different energy levels, volume, disagreements, different humour vs seriousness levels, etc.

See my root-level comment about potentially different behaviour and semantics for neurodivergent :).

I take it to mean upsetting the flow of conversation.

For example, suppose you're at a party, talking in depth about a football team's season and they say something unrelated like "Oh by the way have you seen John?". It is usually a polite way to try to wrap up a conversation. A polite response would be something that graciously gives them permission to change the subject or leave, for example, "I think I saw him outside, maybe go take a look?".

Sometimes it takes the form of bored body language and sentences that don't lead the conversation onwards, e.g. "Yeah that's crazy" or "Well, what can you do...". In that scenario I like to give the conversation a respectable death, e.g. "Well, all we can do is hope for a better season in 2027!".

I take it to mean that non-verbal language like either turning toward or turning away indicates whether the person likes you and wants to be in your presence. If you have a signal that you've built rapport don't screw it up by breaking that trust.

By rapport, I believe the author means non-verbal cues that the other person is interested.

Some cues include the person physically squaring up to you front to front instead of being at an angle to you. Another cue could be touching you on the shoulder or forearm. For me the most obvious tell is that they are laughing or giggling.

Breaking rapport means the other person wants to disengage without offending you. I usually make the excuse I need to take a breather.

i'll give it a shot: you and i meet and start to talk about the weather, then slowly get to some personal questions, and i mention that i prefer quieter places when talking to people.

later, when going out with friends, if i ask "where should we go to talk", and you suggest someplace obviously loud and not great for conversation, this could be seen as a mild form of misunderstanding something i communicated previously about a personal preference in a given situation: breaking rapport

I interpret 'breaking rapport' as doing something that makes the other person feel less connected to you. For example, bluntly contradicting them, dismissing something they said, teasing them when they are not comfortable with it, looking away while they are talking, or turning your attention to your phone. Anything that shifts the interaction from "we are connecting" to "there is distance between us."

It means to disagree in a playful, teasing and confident way. You can even take it to an absurd level: "I like your dress except I hate the color blue."