[css2.2] Suggestion: Add note clarifying root element's margin collapse behavior

[kannanwisen]

Hello CSS Working Group,

In the CSS 2 specification (and inherited by the Box Model module), section 8.3.1 lists "Margins of the root element’s box do not collapse" as a primary exception to margin collapse.

While this rule is correct, its relationship to the general concept of a Block Formatting Context (BFC) is not immediately obvious, and this can be a point of confusion for developers trying to build a consistent mental model.

Suggestion

It would be very helpful to add an informative note to this section that explicitly connects the root element's behavior to the well-defined margin-containment property of all BFCs.

This would clarify that the root element is not an arbitrary exception, but rather the first and most foundational example of a BFC in action.

An example of what this note could look like:

**Note:** The root element establishes the document's initial Block Formatting Context. Its behavior of not collapsing its margins with its descendants is a specific instance of the general principle that any BFC contains the margins of its in-flow children.

Adding this context would significantly improve the specification's clarity for those learning how these fundamental layout mechanics interrelate.

Thank you for your consideration.