1. Would it be possible to make older versions of pdf comments available to import into Indesign? I tried the feature this morning, but it said I couldn't import because it was from an older pdf.
2. It would be nice to have this because not all clients/people in my organizations have access to get updated Adobe Acrobat Pro etc.
By older PDF, it meant that PDF is generated from older version of InDesign, it does not mean that version of Acrobat was older.
There is a workaround to import comments from those older PDFs.
Open indd document in ID 2019, export a PDF from it and then in Acrobat's Comment panel, use its panel menu 'Import Data File' to import comments from older PDF. Now you may use this newly created PDF to import all comments in ID 2019.