If I run a rule like
Individual: @A*
Annotations: rdfs:comment @B*
multiple times, I get the following error:

In comparison, a rule like this can be run multiple times, without any error:
Class: @A*
SubClassOf: @B*
In the case of a class declaration, if an entity that would be generated from a cell is already found in the ontology (and has the right type), the existing entity would be used in the rest of the rule. This is the desired behaviour, and should happen for individual declarations as well (and in the future also for object, data and annotation property declarations, too) .