I have found a design bug. If comments are locked on a question, the "add comment" link is still a link, although it is not clickable and serves no purpose as a link. See for example here What can I do when getting "We are no longer accepting questions/answers from this account"?:
Hovering over the element still produces the link mouse pointer and the link changes its color.
This is related to Tooltip still showing for "comments disabled" text on deleted/locked posts. I would suggest to disable the link behavior and use a different tooltip.