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Makes the summary part of any 'Text area with a summary' field required and visible on the node edit form by default, and sets a character limit on it.
My own use case is on a site with lots of user-generated content which appears in views, using the 'summary or trimmed' display mode. Most users don't seem to notice the 'Edit summary' link above the body field, which means the views end up displaying an often unhelpful trim of the full post. This module forces users to actually summarize what they are posting.