Okay I went and checked the WordPress Meta widget. It has Entries RSS and (all) Comments RSS options only. I also restored an old backup of the previous theme and it had (all) Comments RSS and Entries RSS also although not using the standard WordPress widget. The current theme does not have a built-in option either to display a comment feed link per post although it would be easy to add,
I really am fairly sure I did mention it to you in 2014 and I’m also fairly sure (but not certain) that it was never a link on the site. But my memory is terrible!
I suppose it is theoretically possible a parent theme update added a comments per post RSS link which was then subsequently removed in a later update but there’s nothing in the change log related to that and I would have thought I’d have noticed extra links appear and disappear.