I'm writing a 3rd person limited multi-pov Sci-Fi. The thoughts of whatever POV is being followed at any point are sometimes shown in italicized writing. Suddenly, 42K words in, starting off chapter 11, are four paragraphs of a diary. The paragraphs are written in a different font, one that is clearly handwriting. After the diary entry, the POV is shown to close their diary, and the chapter goes on as normal.
Is a sudden and drastic, yet temporary and brief, format change like this jarring to the reader? The way I see it, it may either be entirely OK, problematic or completely off the table. If the first or last, why?
If it is problematic, how may one do it in a way that works? What does one need to consider? I don't feel like I fully grasp the consequences of doing something like this. I guess it is technically changing the story from 3rd person to 1st person. Then again, visual and narratives clues are given to show the reader that it is more like the reader is given a 3rd person view onto a diary page of the POV. It's not like the POV directly becomes the narrator, it's more like their diary narration is pulled to the forefront of the reader's perspective. But then again, that may just practically be the same thing.