As you can see from pandoc's changelog, the man reader was only introduced in version 2.4. You're using an older version, so...
- Bug#959851: pandoc: $ in nroff table causes spu... James Youngman
- Bug#959851: Acknowledgement (pandoc: $ in ... James Youngman
- Bug#959851: Acknowledgement (pandoc: $... James Youngman
- Bug#959851: pandoc: $ in nroff table cause... John MacFarlane
- Bug#959851: pandoc: $ in nroff table c... Jonas Smedegaard
- Bug#959851: pandoc: $ in nroff tab... James Youngman
- Bug#959851: pandoc: $ in nroff... Jonas Smedegaard
- Bug#959851: pandoc: $ in ... Jonas Smedegaard
- Bug#959851: pandoc: $ in nroff... John MacFarlane
- Processed: Re: Bug#959851: pandoc: $ in nr... Debian Bug Tracking System
- Processed: Re: Bug#959851: pandoc: $ in nr... Debian Bug Tracking System
- Bug#959908: marked as done (pandoc: please... Debian Bug Tracking System
- Bug#959851: marked as done (pandoc: no war... Debian Bug Tracking System
- Bug#959851: marked as done (pandoc: no war... Debian Bug Tracking System
