Sure enough, after a little tweaking to make it work with the Generator friendslist layout (which involved following the instructions in the script, then changing "ul" to "p", and adding "*.livejournal.com/friends*" to the list of affected pages so that it'd also work on "previous" pages), LoudTwitter posts on my friendlist now vanish, leaving just a placeholder of the subject line, date/time, and the links to the full post & the post-a-comment screen--so that I can still go in and read those posts if I choose to do so, but it's a lot easier than it was before to simply skip right past them.
After NoScript, Adblock, and Web Developer, I think Greasemonkey is quickly becoming one of my favorite Firefox extensions.
Feudalism: Serf & Turf