I...guess that's a word for it.
Foglio does draw detailed backgrounds, but at times it feels needless and amateur.
Here, I've combined four arbitrary pages of comics (Lackadaisy, Paranatural, Girl Genius, Dr. McNinja), hopefully a broad enough range of art styles to illustrate what I'm talking about.
Lackadaisy is a work of art. The lighting interacts with the characters and their contours realistically, while also serving to highlight the atmosphere by contrasting the orange incandescent and green.
Paranatural is pretty flat. There is some shading, and while it's far from perfect or detailed, it's consistent and where you would expect it to be (e.g., the tree casts a shadow on the house, the brim of Max's hat, etc).
Dr. McNinja isn't the prettiest one, but there is an illusion of depth and angles on the man's face and paper. Again, it's where you'd expect it to be, and is pretty consistent. Even his legs cast a shadow on the chair.
Which brings us to Girl Genius. The bioluminescence extends in a small circle around it's location, and, except for the scepter, doesn't cast a shadow on anything (see the fish in panel 2, which should have a brightly lit face). In panel 1, Agatha's boobs have shine on them that makes it appear lighting is coming from the right, but her left shoulder is equally well lit. Panel 2 man's shirt has some strange lighting to make it seem like there's wrinkles, but nothing else suggests that. The bottom two panels has clothing lit up anywhere, but it looks like some sections are designated 'light' and others 'dark'. Seriously, look at the clothing, any given color has only two shades regardless of how much shadow should be on it. And this wouldn't be odd, except Foglio puts so many weird dots of light on character's skin, the difference is jarring.
I'd be tempted to say he doesn't understand anatomy and is making educated guesses as to which sections should be lighter.