To varying extents, saying you don't do this is really hard for any third party application integrated into a website. Unfortunately, we can't pull up contextual search results about a text selection without consulting a third party service like Bing or Duck Duck Go, so I doubt that we'll be able to do much better than offering an "opt out" feature in our UI.
> Don't insert text into my cut and paste buffers
We don't currently do this, but if our users ask for it, there is a good chance we will add it. Since it does sound like a frustrating thing, we can push to make it an "opt in" feature on the site owner's side, as opposed to the default behavior. At least that way, it'll only happen when the site owner really wants it to.
> Don't steal my search abilities
I don't believe we currently inhibit your ability to search with your engine of choice. If you find that we do, please let me know!
> Don't steal my mouse clicks
We don't "steal" your mouse clicks (though we do listen to them ;), and we do try to make sure the window only pops up when you have selected text. This experience will hopefully improve over time. Unfortunately, not doing this prevents the app from working in the first place (unless you have a better way to implement it)
> Don't pop up windows
Again, not doing this makes it difficult to have the app in the first place. I know its not for everyone, but a lot of our users really enjoy this functionality.
> Don't break my browser
That's something I can definitely do. Please let me know if you notice us breaking your browser in any way :) us not breaking your browser is one of my highest concerns.