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Iteratively using the source view control over and over will cause spurious paragraph nodes containing a non-breakable space to appear in the document. Each successive cycle causes these elements to duplicate, rapidly corrupting the document
The issue appears related to auto-paragraphing. Only certain tags are affected, seemingly based on how they are defined within the dtd. Note that randomly generated tags such as "broken" also introduce the behavior.
The issue is entirely absent when switching enter mode over to BR.