Using moderation tools or policies to prevent duplicate contributions in online communities
Using moderation tools or policies that flag, delete, or merge duplicate entries and notify the users who created them.
For example, the following screenshot is from StackOverflow.

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Tags
Library Science
Online Communities
CSCW (Computer-supported cooperative work)
Computing Sciences
Related
Using a search function to prevent duplicate contributions in online communities
Showing warnings or alerts to prevent duplicate contributions in online communities
Using moderation tools or policies to prevent duplicate contributions in online communities
Rewarding users who contribute entries
Developing social norms that prevent or discourage duplicate entries in online communities
Providing suggestions or recommendations of similar or related entries through search engines in online communities