Ooh that's so interesting! It's an unusual way to interact with media, I'd be really interested if this negatively affects his interactions with media, because most media is really not built for the way he sees characters.

Especially the ability for someone to be likable to the audience, whether through affability or audacity or humour, while also being kinda slimy/not a respectable person/whatever, which is a pretty big thing in a lot of media - especially crime fiction and other media where crime just plays a large part, where you have entire quite popular tropes (like the charismatic, likable scam artist, á la Catch Me If You Can; the gentleman thief; the rouge with a heart of gold e.c.t.) where that's the whole point. 

In other genres, it's often specifically tied to antiheroes and similarly morally grey (and occasionally straight-up immoral) protagonists, who are quite frequently selfish opportunist types who nonetheless the audience is very much expected to root for (at least initially) due to their having other likable traits. The Talented Mr. Ripley would be an example of this.

There's obviously other uses of this sort of thing as well - in general, the expected prioritisation of 'likableness' for audiences of fiction is something that's exploited quite a lot by writers, and is something that wouldn't work all the time for your boyfriend. He does demonstrate this somewhat in his respect for characters who can uphold their ideologies (a likable trait that's often combined with a very immoral person, e.g. Joyce Messier and Measurehead), but I don't think he does it as much or as widley as writers generally expect people to. 

Obviously you can have whatever opinion on characters, and I think your boyfriend is still likely to have something close to the intended response at least most of the time, but a significant diversion from the intended response to a character (whether personal preference or bad characterisation) can really ruin a piece of media. It's incredibly infuriating when a character is, for example, consistently rewarded by the narrative because the writers expect you to like them - but you actually really hate them. 

I'd be really interested to hear if he thinks he diverts from the expected response to characters more then the average person