Passing the word - got this from
theeverdream.
To disable crossposting:
.b-repost-item {display:none}
1. Go to Customize Journal Style (Customize your theme)
2. Select Custom CSS from left hand sidebar menu
3. Paste the .b-repost-item {display:none} into the Custom stylesheet box.
4. Save changes!
...I'd add 5. Rejoice! to the end of that list there. Hopefully this isn't something that LJ's going to notice, call a glitch, and 'fix.'