How important is staying away from author intervention in fiction?
I don't do it much, but for things like creating the setting/scenery I do. I kind of go from third person omniscient/author intervention to third person limited. I don't give away future information, I just set the scene.
I'm guessing you're referring to authorial intrusion. The Swainettes will tell you it's bad thing but that's just because it doesn't fit with the rules they take as their gospel.
If it is your style for the author to provide commentary and reaction, then its your style. Authorial intrusion is a bona fide literary device.
Technically, authorial intrusion is one of the telling sins but if the intrusion is your intention then no harm no foul.
