[Aachen]

Don't have a computer handy to try, but it can block elements right? What if you block simply dialog (without # or so, because it's not an ID but a tag name) on the desired domain?

Or a little userscript walking the DOM to find dialog elements and removes them. Or you could check if one can listen on them for show/open events, or hijack the show() method to do nothing

Lots of options I'd say

Not something I'd have in mind when using dialogs for legitimate purposes as a developer though. Don't wonder why you don't get my "do you really want to delete this item?" on my software when you block these altogether, but I guess you mean this for specific domains where it's used for ads (have yet to see dialog used for that, but no surprise that they'd exist)