I also just disabled the "Opera AI Prompts" extension:

Same result: the garbage button is there, not allowing me to resize the comments field:

@leocg as mentioned, it is. Here's a screenshot:

Or are there any hidden settings that I'm not aware of?

Despite having turned off all the AI bullshit features, the annoying button is still there. I saw that others complain about it and there's no workaround.

This bug isn't about that. It is about the fact that when the button is there, it overlays resizing. This is a problem for me in GitHub comments (in code reviews). Screenshot attached:

Even in the very edge of the corner, the button overlays the resize handle, which makes it impossible to resize. In other words, it breaks the website functionality and there's no way to opt out or dismiss this useless thing.

Please fix it.