I had a similar experience recently with a question I had answered years ago. A highly ranked user came in, complained in a comment about the fact I linked to documentation instead of copy pasting the docs into the answer then downvoted me causing a loss of 2 karma. I reported the comment because it was ridiculous this person is scanning questions which are years old to try and find things to nitpick.
I'm not sure if they removed the comment or if some other moderator did, but it was gone within a couple of days. My karma loss remained. It's absolutely ridiculous over there sometimes and these sorts of interactions are one of the big reasons I stopped participating.
The best practice in this case is to edit your answer to include the docs as well as the link, so the next user can find the answer in one place, preserved even when external links inevitably break, change, or disappear over time.
A good citizen would remove their downvote after you did that.
A better citizen would have just made the edit themselves to help everyone.
I'm not sure if they removed the comment or if some other moderator did, but it was gone within a couple of days. My karma loss remained. It's absolutely ridiculous over there sometimes and these sorts of interactions are one of the big reasons I stopped participating.