It was not hidden because of the basilisk, but because it was a reply to a -4 post. It is no longer invisible on the user page. You can test my claim by downvoting the parent to -4 and reloading that user page.
I COMMIT TO UPVOTING EVERY HIDDEN COMMENT.
Please don't. This feature is a heuristic for reducing low-quality clutter (in the global comments feed and on the post pages). Assuming it usually works, precommitting to upvoting hidden comments amounts to precommitting to reducing of the average quality of the visible comments.
(The hidden comments are visible under the "comments" tab of user pages, just not under "overview". Wei's tool can be easily fixed to look at that page instead of "overview".)
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.