Zero component abstractions
With ECSS, if a component needs to be made that is similar, yet subtly different to an existing component, we would not abstract or extend from this existing component. Instead, a new one would be written.
Yes, I'm serious.
Even if 95% of it is the same.
The benefit of this is that each component is then independent and isolated. One can exist without the other. One can change however it needs to, independently from the other. Despite their apparent aesthetic similarity at the outset, they can mutate as needed with no fear of infecting or tainting any other similar looking component. To extend the biological metaphor, we have gained components that are self-quarantining by virtue of their unique namespace.
Note
A further analogy: A BMW 3 series has a lot in common with a BMW 5 series. But they are not the same. They may share some/many parts (the equivalent of CSS property and value combinations) but that doesn't make them the same. Their differences...