She's got severe communication disorder, and suffers from extremely bad social anxiety around other people. I might be remembering wrong, but I think this is the first actual time she talks to anyone in the manga, which is huge.

As the series goes on and Tadano + friends interact with her, she has more and more moments where she talks normally. They're mostly only when it's just her and Tadano, tho. The rest of the time it's thru notebook and body gestures.

So yeah, Jyron is more or less correct in his assumption. Is cute mango.

All the pictures uploaded here led me to half-believe that Komi was a borderline selective mute that primarily communicated through wide-eyed stares, narration boxes, and the occasional written note.