Stack Overflow is a Q&A site where knowledge entities are presented in the form of questions and answers. Stack Overflow does not allow duplication of knowledge entities. This is enforced through a variety of methods. 

Stack Overflow's Treatment of Duplicate Knowledge Entities

Reddit does not have a monolithic policy concerning duplicate knowledge entities. In some cases, duplication is allowed; in other cases, it is not. It largely depends upon the community and moderator.

Reddit's Treatment of Duplicate Knowledge Entities

- Stack Overflow
- Quora
- Reddit
- Wikipedia
- etc

San Jose State University

Duplicate knowledge entities in online communities occur when multiple sources—such as articles, books, websites, or videos—repeat the same existing knowledge. Two entities are considered duplicates if their core topics are identical, even if they are not exact, 100% copies of one another.

Duplicate Knowledge Entities in Online Communities

- Content quality control
- Limit resource cost
- Limit conflicts among users
- Protect Reputation

Why do online communities discourage generation of duplicate entries?

- Disconnected Knowledge Entities
- Stand Alone Learning Content

Causes of Dupicate Knowledge Entities in Online Communities 

Duplicate knowledge entities can be used to create an illusion of credibility, where false or misleading information is repeated enough times that it becomes accepted as true. This may create the perception of consensus and credibility around false or misleading claims. This is particularly problematic in the case of disinformation, where the intent is to intentionally deceive or manipulate an audience.

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