One of these tweaks was getting rid of an extra border which was rendering under the comment area. However, I took off too much and ended up removing borders from other applications.
I think we don't actually need this setNoBorder() stuff after all -- a later change was sufficient to stop the actual border I was trying to get rid of from rendering. So this mostly just reverts part of D19660.
This rendering still isn't perfect, but I'm fine leaving that for another day for now.