IT WORKS! HALLELUJAH IT WORKS!

The only problem I have with it is that the toolbar icon doesn't make it clear whether it's active or not. It should be more clear, at the least, the tooltip should clarify it.

This is the only addon (and I've tested a lot) that actually blocks YouTube videos from autoplaying the next video in a playlist on the YouTube site itself but doesn't block them from autoplaying in an embedded frame. Thus, it works perfectly to allow watching videos on YouTube without losing your unfinished comment because stupid YouTube autoplayed the next video before you could submit the comment, while also letting you watch videos in an iframe while you work on other stuff. 👍

Of course, how long it'll work is anyone's guess since as I type, Google is probably actively trying to figure out ways to break this and FORCE autoplaying no matter what users want or how inconvenient it is or how much of users' bandwidth it wastes, because they don't actually care if people watch videos, just that the videos run so that ads run so that Google profits. 😒

Until then, thanks a lot T Rich for this addon; I won't have to worry about wasting my time from lost comments due to autoplay for a while. ❤️