Hi! Thank you for your review. Which permissions are unnecessary?

Unfortunately, in order for Rikaichamp to be able to present pop-ups on the page it requires access to that page's contents. Web extensions do not provide any more fine-grained permissions that that. As far as I can tell, it's impossible to create a pop-up dictionary with fewer permissions.

The source code is available for audit and/or forking if you are concerned about misuse of those permissions.

I think that's clear from the add-on description (there is no hovering on touchscreens) so I don't think a 1/5 rating is fair.
That said, I'd like to make this support Android some day so perhaps we can address touchscreens at the same time.

Update: It now has first class support for touchscreens.