Compare your watched and watchlist between users and friends.
When you're looking at other users pages, the purple checkmarks, the blue list icons and such refer to your watched history not the other user's.
Was that what you meant?
What you're describing I think works well and as intended.
I'd like a page where I can select another user and I can get a comparison of watched time, most watched movies for example. Or a page where I can compare my watchlist with that of another user and see if there are common items and how long they've been on the list, stuff like that.
Perhaps something like what myanimelist.net has, would be nice: if you visit another persons profile, you see their affinity to you.. I have no clue how it's calculated. And you can also see the shared anime and how you both rated it, and the ones that are unique to each you, and the other person.
Example of mine and my friend who's also on Trakt (non-VIP):
That's correct, I'd like a way to know which movies a friend has watched that I haven't or the opposite, and possibly compare ratings.
Same for TV shows, but in that case it's probably easier to compare progress.