While YouTube does allow users to leave comments that include the timestamp, sometimes you have to go hunting for it, and not all users bother either, but that could change in the future. It would seem that according to a YouTube support document, the company is now testing a timestamp button that allows users to leave comments at that particular point in the video.
According to YouTube, “We’re testing out an easier way to add a video timestamp tied to the exact moment you’re watching when commenting on a video. People in the experiment will see a new icon as they’re writing a comment that they can tap to automatically add the current time of the video (without having to manually enter it themselves!).”
YouTube has been making an effort to make its videos more contextual, and recently the company had also announced that they will be testing out the ability for AI to help automatically generate chapters so that users can skip ahead to parts of the video that they want.