Standard for abbreviated license: CC BY-SA or CC-BY-SA
Yes, agree that we should follow CC convention and leave the CC unconnected. I'll make the necessary changes.
You are right. The table is more about compatibility. The note you added to explain that PD is not a license takes care of the issue for me.
I did now notice, however, that the rows and columns have different ordering. PD is first in one and last in the other. I recommend that PD be moved to be listed first in the columns. (This seems better than moving PD to be last in the rows because I think the juxtaposition of PD and BY is useful, and the table has a feel that it moves from more to less open.)