LHF is a small Firefox extension to remove the "flicker" effect from the "hide/collapse thread" functionality on the lulz.net/furi/ imageboard.
Download/install (version 0.2.1, Feb 7 2012)
Source (technical readme)
To use, just install it, restart Firefox, reload a page with collapsed threads, and the threads should stay completely collapsed without reappearing for a split second. I don't claim to know a lot about Firefox extension development, so I welcome bug reports, advice, criticisms, etc. If you just yell about it on lulz, I'll probably see it.