I felt/feel the same, but I am greatly comforted by the add-on making an attempt to clearly communicate what it uses/needs each of those permissions for: https://addons.mozilla.org/en-US/firefox/addon/tridactyl-vim...

Even though there’s no guarantee that the explanation corresponds exactly to what is implemented behind the scenes, this unusual pattern of user respect and consideration makes the add-on/developers feel more trustworthy than other sketchier ones.

This is about the only type of addon that genuinely needs full access to everything - the type that replaces your browsing interface. It needs to be able to interact in all the possible ways with every single element on the page. There's no way around it having scary powers, because using them is its base purpose.

I'm really glad that other people feel that permissions over-reach is a problem.

Specifically in the case of Tridactyl, as an interface to the entire webbrowser is needs access to the entire web browser. It does manage bookmarks, it does modify webpages (by adding link hints).

It's open source, just read it and use the source-code release https://github.com/tridactyl/tridactyl