I tried to crosspost this to Facebook...nah, I'm kidding.
I found this via
gwai_lol:
"To get rid of the twitter/facebook repost links in your journal entry comments do the following:
1. Go to your "Journal" menu, and select "Journal Style"
2. To the right, you'll see what theme you're using, with a link stating "Customize Your Theme". Click that link.
3. Scroll down a little ways, and you'll see that on the left side of your screen, you have multiple options to modify your theme. Click on the "Custom CSS" link, and it should load the options for doing Custom CSS.
4. From here, all you have to do is go to the "Custom Stylesheet", and put in this line:
.b-repost-item {display:none}
Once that's in there, you want to save the changes, and you should be done. Leave everything else as it is."