“Youtube Username” *ago site:youtube.com/watch. However, testing it out on some of my accounts only turned up videos I had commented on years ago and nothing recent. The other alternative is the man is psychotic enough to search through your liked videos and find your comments, or has a bot do it for him.

I know you can look up your own comment history fairly easily. But it's supposed to be secure for only your eyes.

The YouTube app recently added an update that lets you view all of a person's comments on YouTube when you click their name in the comment section. Not sure why they did this, or if this will be going live on desktop too.