Raw / Source of comment. #4714

If you are a collaborator on a repo you can click the edit button to see the source. For other comments we'd have to make an API request.

It doesn't sound terribly difficult but also maybe it's not super useful.

For your specific use case, I usually select and press the R key. GitHub will try to preserve the markdown (in reality it converts the DOM into markdown, so it won't be a 1:1 match of the source)

closing as wontfix for not enough demand

The process where it goes from a 'good idea' to 'barely meets the bar', by the time you write the issue.