The phpdocumentor team has implemented a parser for rST in their phpdocumentor/guides package that is much more spec compliant (and more extensible) than doctrine/rst-parser (they initially planned on forking the doctrine parser to improve it, but it ended up as a full rewrite as things were too messy internally).
The Doctrine team has already migrated the Doctrine documentation to use phpdocumentor/guides as parser. We plan on abandoning doctrine/rst-parser in the future (the main blocker being the Symfony documentation that is not migrated yet).
It would be great if your project could migrate to use phpdocumentor/guides as parser.