The idea behind DISC (as referenced in the article) is that there are four behavioral axes, and that by learning to understand which a person ranks highest and lowest on (via reading body language, speech patterns, expressed preferences, etc), you can modify your behaviors in context to them in such a way that the way you treat them is the way they want to be treated.

The core thesis of DISC is that there is not a "normal person" (even though we intuitively think there is). Rather, there are normal archetypes of people, and understanding those archetypes makes it easier to interact with them. You assert that "most people in most circumstances want minimal interaction with strangers", but this is wholly untrue (and indicates that you are a relatively low "I", which is fairly typical of tech types). Some people actively seek out interactions with strangers (strangers are just friends they haven't met yet!), and understanding that makes it much easier to interact with and communicate with them. High-I types actively seek and crave social interaction. They may modify their behavior to the situation, but they are most comfortable when they're socializing; in fact, the further someone's adapted (environmentally-imposed) behaviors are from their natural (preferred, given a lack of other constraints) behaviors, the unhappier they tend to be. While it may be culturally verboten to strike up a conversation with the person next to you on the subway, the high-I would like nothing better than to chat about their day with the person next to them (and the low-I wants nothing more than to be left alone).

Since there are only these four major attributes to learn, you can read people that you don't know intimately - sometimes from across the room!

For example, if you can recognize a high "D" personality (which is frequently easy to recognize, but also relatively rare), you will make them feel most at ease by not having to be in charge of an interaction - behaving cooperatively and deferentially will make it much easier for them to feel comfortable with you than if you are attempting to be in charge. This doesn't mean to be a doormat, but simply that if you can give up some non-critical control, they will feel that the interaction is much more "natural".

By the same token, interacting with a low "D" requires you to step up and take the reins. Being assertive and confident with a low D will result in a smoother experience, because their natural tendency will be to be deferential and unassuming, and it's actually more comfortable for them to be given some direction and to have someone else make the decisions.

Think about the age-old "where do you want to go for lunch?" question. When interacting with a high D, make suggestions, give input, offer opinions, but try to let them make the decision. When interacting with a low D, you might need to be the one to define the boundaries and make a decision about where you're going to go. The high D doesn't like other people making decisions for her, and the low D doesn't like having to be the one on which the decision rests. Understanding that lets you interact smoothly with both of them, even though they require diametrically-opposed approaches.