Idk why people think Komi is boring and retarded. Despite her lack of verbal communication, she still does a lot of physical, gesture communication. Her range of emotion is just like anyone else (sadness, surprise, anger, etc). If you think Komi doesn't do anything to deserve Tadano, just a friendly reminder that she took care of Tadano when he's sick even when he tried to tell her to not bother herself with him. She also cheered him up during a Karaoke session when no one paid attention to him. In a recent chapter, she even improved herself from the invited to the invite"r", with her actual voice too.
Manbagi so far has been a tsundere to him for the majority of the time. Tsundere may look cute in anime/manga cuz at least you see the cue of what they think. In reality, if you see someone acting like that. (punch, insult or deny your good intention toward them) it will be a massive turn off. You don't think or say "you're so cute" when the person yells at you "Don't look at me like that!" or "Shut up!". I don't say Manbagi is a bad character; she is a good person and a good friend. But to say that she has done more to Tadano to deserve him more than Komi, I would like to take a small step back and reevaluate it.
Anyway, Tadano has been a great friend with everyone. He so far has the most contact with Komi; he seems to harbor more affectionate feeling towards her than Manbagi. But hey, life is strange and he can go in any direction. I don't think he and Manbagi will be a bad couple at all. (I still like Komi x Tadano more XD