Thanks for sending the file.
The comment also does not show up in Photoshop, Adobe Bridge, or File Explorer's Comments column or Properties dialog either.
(Telling File Explorer's Properties dialog to remove all personal data also does not remove the field from the file.)
It's using the old JPEG Comment field, rather than an EXIF tag or similar. My understanding is that JPEG Comment is rarely used/displayed these days, at least for anything useful (or if it is used for important information, the information is usually written into an EXIF tag as well). If Photoshop won't show the field then I think we can consider it obsolete.
However, you can use ExifTool Custom Columns to add columns to Opus based on data that ExifTool can see, which should give you a workaround if you need to see that data in Opus.