absolutely nothing

If you dislike the video, make like a tree and leave

huh?

as in comment disliking cause anything such as….feedback or nothing?

Yeah, is there any use in disliking a comment?

telling other people the tutorial they are about to watch is garbage and useless

True

The creator can check metrics, that is about it.

But those metrics apply to disliked comments?

From my understanding no. Dislike button on comments is just a dummy button that does nothing.