It's probably an adblocker, I explained why they get misaligned ([is-in-first-column] attribute adding extra margin) if a video gets hidden and the rest flow to fill in its place here:

https://news.ycombinator.com/item?id=43848061

This bit of information makes the entire thread hilarious to read.

Bunch of hackers using adblockers that modify the client-side UI to cheat Google out of money and then complaining loudly about a minor UI convenience. How dare Google not optimize for them!

I say this as someone who uses an adblocker myself. But come on.

Hehe, you need to be a big enough nerd to know to do this when you see it's misaligned:

https://github.com/insin/control-panel-for-youtube/blob/cf18...