How odd. I don't think it's limited to people who post videos, because I was getting notifications about replies to my comments before I ever posted a video.

In the notifications settings, do you have a heading that says "Comments & Activity"? Because that's where you turn on notifications about replies to your comments. "Activity on my comments on others' videos" is the setting to turn on.

(scratches head)

Anyway, I love the effects you get.

Thank you! This stuff is addictive.