BERLIN—When German social-media app Jodel was five months old, its founder Alessio Avellan Borgmeyer noticed a potential problem: while more people were logging on, a small number of users weren’t the community he had hoped to attract. They were posting offensive comments and pressuring other users to submit naked photos.
Apple Inc. also saw a problem. The naked photos violated its rule on sexual content, and in early 2015 it kicked Jodel Venture GmbH out of its app store for a week.
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