This change was first proposed by Small (1903) based on morphological differences with the rest of the genus, and has been supported by experiments which demonstrated that this species will not cross with other species of Campanula (Gadella, 1964).
Unintended disagreements occur when a parent (B) is
thinned by swapping a child (E) to another part of the
taxonomic tree, resulting in existing IDs of the parent being interpreted
as disagreements with existing IDs of the swapped child.
Identification
ID 2 of taxon E will be an unintended disagreement with ID 1 of taxon B after the taxon swap
If thinning a parent results in more than 10 unintended disagreements, you
should split the parent after swapping the child to replace existing IDs
of the parent (B) with IDs that don't disagree.
Corey, I had already drafted this change (you should have seen a caution statement when you created yours). I added the source citation to yours.