[css-anchor-position] Rephrase the skipped-contents prevention to be directly in terms of skipping, rather than making things relevant, as that better maps to the spec concepts. w3c#10184

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -448,17 +448,22 @@ in ''anchor()'' and ''anchor-size()''.
 <h3 id=anchor-relevance>
 Anchor Relevance</h3>
 
-As long as an [=anchor element=]
-is a [=target anchor element=]
-for any positioned element
-that is [=relevant to the user=],
-the [=anchor element=] is also [=relevant to the user=].
+When determining whether an element |el| is [=relevant to the user=],
+if a descendant of |el| is a [=target anchor element=]
+for a positioned element
+who is not [=skipped contents|skipped=]
+and whose containing block is not |el|
+or a descendant of |el|,
+then |el| must be considered [=relevant to the user=].
 
 Note: This means that, for example,
 an anchor in a ''content-visibility: auto'' subtree
 will prevent its subtree from [=skipping its contents=]
 as long as the positioned element relying on it
-is [=relevant to the user=].
+is also not [=skipped contents|skipped=].
+(Unless the anchor and the positioned element
+are both under the same ''content-visibility: auto'' element;
+they can't cyclicly keep each other visible.)
 
 
 Anchor-Based Positioning {#positioning}
@@ -1012,6 +1017,18 @@ the ''anchor()'' function resolves to its specified fallback value.
 If no fallback value is specified,
 it resolves to ''0px''.
 
+
+<!-- Big Text: visibility
+
+█▌   █▌ ████  ███▌  ████ ████▌  ████ █▌    ████ █████▌ █   ▐▌
+█▌   █▌  ▐▌  █▌  █▌  ▐▌  █▌  █▌  ▐▌  █▌     ▐▌    █▌   ▐▌  █
+█▌   █▌  ▐▌  █▌      ▐▌  █▌  █▌  ▐▌  █▌     ▐▌    █▌    █ ▐▌
+▐▌   █   ▐▌   ███▌   ▐▌  █████   ▐▌  █▌     ▐▌    █▌    ▐▌█
+ █  ▐▌   ▐▌      █▌  ▐▌  █▌  █▌  ▐▌  █▌     ▐▌    █▌     █▌
+ ▐▌ █    ▐▌  █▌  █▌  ▐▌  █▌  █▌  ▐▌  █▌     ▐▌    █▌     █▌
+  ▐█    ████  ███▌  ████ ████▌  ████ █████ ████   █▌     █▌
+-->
+
 Conditional Hiding: the 'position-visibility' property {#position-visibility}
 ------------------------------------------------------