Since I don't really like the bugtracker, I'll post this here so someone can check if it is there yet (wasn't last time I went through them).
I filled one of my compost bins to 100% two nights ago. Last night I check and it was 98%, so I added to it and brought it back to 100%. Tonight it was 98% again, added to it to make it 100%. Note I have taken no humus from it at all in these past few days. It is untouched by anyone inside my walls that I share with no one. Not a big deal so I didn't want to start a whole thread on it, but thought I'd mention it.
Update: Tonight it was once again at 98%. Instead of adding to it I left it at 98% to see if it will be lower tomorrow. I got a second bin up to 100% so we will see if it too goes down. (I'm not touching the humus in either bin at all)
Last update: after a couple more days it seems the bins drop to 98%, but do not drop lower if left alone. Both the bins were 100%, after a day 98%, the following days stayed at 98%.
So bug, yes, but a tiny little one that I can't see causing any trouble if it stays unfixed.