Opera can sometimes glitch out with 4-ch... Specifically, the Opera 9 preview has problems with the "expanding text box" Javascript here (it doesn't let you type in the comment box). This may only be an issue with the Mac version, but I haven't looked into it much.

Anyway, if you have this problem, I've written a little User Javascript that solves the problem...

// ==UserScript==
// @include http://4-ch.net/*
// ==/UserScript==

window.opera.defineMagicFunction('size_field', function(f,l) { });

Drop that into a .js file and save it someplace handy. Then go here http://www.opera.com/support/tutorials/userjs/using/#writingscripts if you don't know how to tell Opera about your .js files. Voila! 4-ch goodness in Opera. ^_^