After much fidgeting about with Facebook's markup, I believe I have found a way.
For all the situations I have tested it in, this method has worked. So here's how you can get a link to a specific comment:
Below every comment in Facebook, is a little stamp that tells you when the comment was posted.
As circled above, if you right click on that time stamp, and then pick
Copy link address (in Google Chrome) or the equivalent in other browsers, you will then have the link to that specific comment.
Now paste the copied link into your URL bar and you will see the window scroll to that comment and the same comment will be highlighted for a few seconds.
From a technical perspective, if you are interested in knowing how this works, read on...
Every comment in Facebook has a
comment_id. If you add the
comment_id for a specific comment into the query string in the URL, you will see that comment get highlighted.