I've search for a solution for this specific problem.
When I'm commenting code in a pull request as a reviewer. I can only comment on a single line.
This generates a comment with a snippet of aprox. 4 lines of code which in most cases confuses more than it helps.
I would like to be able to select multiple lines and comment on those. This functionality already exists outside pull requests. If you go to your repository and finding some code in a file, you can select multiple lines.
This has been my workaround, but it is very time consuming because you have to open a new tab, find your repo., find the correct branch, click your way to the right file and finally mark the wanted lines, and copy permalink. Then back to the pull request and paste the permalink. This will create a code snippet.
But this workaround does not apply on deleted lines. Only the current code of the changed branch.
I've found two cases of same problem within both Github forums and StackOverflow.
Thanks for this feedback! We're always working to improve GitHub and the GitHub Community Forum, and we consider every suggestion we receive. I've logged your feature request in our internal feature request list. Though I can't guarantee anything or share a timeline for this, I can tell you that it's been shared with the appropriate teams for consideration.
Please let me know if you have any other questions.