I am trying to use quotation or blockquote in a document, but when selecting and copying the text in poppler/pdf.js I get double marks.

Looking at the minimal example below:
\startquotation Hello world! \stopquotation
\startquotation Hello world! \stopquotation
\startquotation Hello world! \stopquotation
\startblockquote Hello world! \stopblockquote
“Hello world!”\\
«Hello world!»\\
‘Hello world!’\\
\startquote Hello world! \stopquote\\
\quote{Hello world!}\\

The text stream seems to have an additional object for the quotation and blockquote lines.

Rendering the PDF in itself is fine but when copying the text I get mixed results (poppler/evince and pdf.js give double marks but mupdf does not: “Hello world!””,«Hello world!»»,‘Hello world!’’,‘Hello world!’’).

Is this just an issue with poppler/pdf.js when trying to extract the text (as the PDF rendering seems all fine)?