Share common policy or capability when its consumers are meant to change together. Similar code alone does not establish shared authority or a shared reason to change. Keep independent commitments free to evolve independently.
Why: a helper can acquire accidental authority when unrelated features must negotiate with it merely to preserve reuse. Conversely, duplicating one official policy lets its intended consumers disagree.
Consequence: preview wording and archival wording may need separate leaves; badge and manifest identifiers may need one shared policy. Sharing vocabulary, code, policy, state and deployment are separate decisions.
A current semantic boundary or substitution requirement can justify one implementation behind a contract. Hypothetical future flexibility cannot. DRY (Don't Repeat Yourself), KISS (Keep It Simple) and YAGNI (You Aren't Gonna Need It) are aids to judgment, not higher authorities than the promised behavior.