Sure, it might seem like a dull topic to some, but panel borders can be a significant asset or liability in comic storytelling. When done poorly, they're obvious and distracting, but when they're done right, they're completely invisible and seamlessly blend into the story. In an attempt to understand why some panel borders work and some don't, I pulled out a few dozen random comics and spread them out side by side on my table. It's interesting to see the many variations in gutter size, panel spacing, line thickness (or complete lack of line). Some gutters are white, some are solid black, others are filled with various colors. Give it a try sometime, you'll be amazed at the many variations.