YAML filter does not escape special chars in plain scalars on merge...
Issue #1050
new
From the WIKI:
Wrapped lines in the original source document will be unwrapped in the target document. That is, all text will be on a single line. If an illegal character is introduced the user will need to manually add double or single quotes so that the target YAML file is valid. A WARNING will be issued by the filter if this scenario can be detected.