I can’t find this in the Feature Requests (doesn’t mean it’s not there).
Waveform dB needs dB markings down as well as up.
Koz
+1
I’d never noticed that …
+1
I’ve noticed it, but I thought there could be some good reason for that… well maybe not 
I bet I turned over a rock.
Did you know that the bouncing bar sound meters only measure the positive parts of the sound? I found this out when I created my LRMonoPhase test sound track. I turned over one half of the stereo track and the meters were different. They can’t be different if they’re measuring the absolute values of the sound.
The world’s professional sound meters are all very clear that it doesn’t matter which direction they’re connected.
Koz
This was entered in bugzilla on Nov 19
http://bugzilla.audacityteam.org/show_bug.cgi?id=259
and resolved on Nov 28.
So it is fixed in 1.3.13 alpha.
– Bill