For what it's worth, rather than "the rule becomes obsolete" I like to think, "the arrow disappears."
The arrow represents the rule, the logical relation between the the two conditions. For me, "the arrow" is more concrete than "the rule". When the rule is embedded in a chain of rules, such as "A --> B --> C --> D", thinking of one of the arrows disappearing makes the change clear. In the example, suppose we learn that B is false. The sufficient has failed for the B --> C rule, so that arrow disappears, leaving us with A --> B; C --> D. For me, this is easier than drawing consequences from "B --> C is obsolete."
Comments
The arrow represents the rule, the logical relation between the the two conditions. For me, "the arrow" is more concrete than "the rule". When the rule is embedded in a chain of rules, such as "A --> B --> C --> D", thinking of one of the arrows disappearing makes the change clear. In the example, suppose we learn that B is false. The sufficient has failed for the B --> C rule, so that arrow disappears, leaving us with A --> B; C --> D. For me, this is easier than drawing consequences from "B --> C is obsolete."