How do I reference a specific issue comment on github?

I'm trying to refer to a specific issue comment on github, in my readme. But I can't find any information on how to do that (here for example). I know that it's possible to link to issues, but is it possible to link to specific comments in that issue?

You can click on the date in the header of the comment to get a URL to the comment

For example, for issue https://github.com/centic9/jgit-cookbook/issues/5 one of the comments has the following link: https://github.com/centic9/jgit-cookbook/issues/5#issuecomment-51084491.

Simple method:

Every comment in github has header like below

[Commenter Name] commented on [x days ago]

Right click the date information i.e. [x days ago] and copy the link

Since August 2018, there is a more intuitive (and likely more reliable) way.
See "Copy the URL of a comment":

Previously, in order to grab a permalink to a comment within an issue or pull request, you’d need to copy the URL from a comment’s timestamp.

Now you can click Copy URL within the comment’s options menu to quickly copy the URL to your clipboard.

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This works on commits in a Pull Request too:
https://github.com/moby/moby/pull/37558#discussion_r211356672 refers to:

And since February 2019, that works on mobile too!

Issue and pull request comment permalinks can now be copied on mobile devices, via the comment action menu.