On the first item - never tried it.
 
On the second, you are correct.  When deleting an SO line, the associated lines are deleted (the software asks if you want to), but on a PO, you have to individually delete each line - seems like it ought to work like the SO.

I had an existing PO with 2 items on it.
 
The first item had a second description line and 2 lines of specifications.
There was then a blank line, and then  a second line with no extra lines.
 
I inserted 4 blank lines before the first item.  Each time I clicked "Ins Line", I pressed enter 4 times.
I then went back to the first line and put in the Same item number as the one that I moved down.
 
I just tried this again, the way I describe it above (only I have 1 line item), and only the first description line is brought into the PO.
 
BTW: I am using Classic, have not tried it in EVO

Thanks for the link.
That is exactly what I thought ( a couple of old, dormant brain cells fired off while I read that post ).