Acting isn't always realistic, and actually this is something I like. Obviously it works most readily in comedy, but it can be interesting anywhere.

When actors go through a scene, they aren't just calling its real equivalent to mind - or a believable equivalent. They're also commenting on a moment that people will recognize. One way or another, every single acted moment plays on recognition - of similar moments, whether real, fictional, or thus far purely imagined, or before today never once imagined, and now for the first time in some audience member's mind. I mean, that's what acting and art in general do, right? They don't have to be realistic, just evocative - somehow interesting and engaging and compelling.

Because acting is also commenting, it's quite acceptable for acting to diverge from realism - in some sense, the divergence is the comment.

Sitcoms do this all the time. People say things in an exaggerated tone that gets the context in that character's mind across loud and clear. And often this is important, and works, because of the ironies - the contrasts between the situation as we in the audience see it, and how the character sees it - which is a comment both on that character (whom we may love by now) and on the situations we know and are reminded of ourselves. So divergence from what someone in the audience would intuitively expect can be a comment on the character or on the situation. In both cases, it's a comment on the audience members' own lives.