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Right now this is expected behavior when our product WProofreader creates extra spans in CKEditor 4 for its markup, and we can't fix this based on the current product mechanics. On July 2019 we plan to implement a new approach of the WPoofreader work, which should resolve such type of cases. We plan to add our markup on a separate layer separate from CKEditor. However, deadlines can be shifted due to tasks with more higher priorities. We will inform you once a new mechanism will be released.Removing spans:
As for now, you can add some extra code on your side to clean spans. For example, you can use a "removeMarkupFromString" command.
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