This extension steals money from sellers by inserting itself as the referral to every purchase you make. If you got referred by another source (e.g. a YouTuber you like; or a friend of yours), Honey will replace the real referral with themselves, effectively stealing the commission from your friend / YouTuber / etc.

Aside from that, in my experience, Honey has never, ever found a discount for any product I've purchased; although it has worked sometimes for some people.