A separating pronoun can also help distinguish a predicate from an adjectival modifier. This is relevant where the surrounding nouns could otherwise be understood as part of one descriptive expression rather than as a complete predication.
زَيْدٌ الْفَاضِلُ
Zayd the virtuous / Zayd is the virtuous one.
زَيْدٌ هُوَ الْفَاضِلُ
Zayd is the virtuous one.
Context may create ambiguity in the first expression. The second more clearly marks the subsequent expression as a predicate in the intended analysis.