Oddly enough I didn't even touch that part of SMF "out of the box" -- and for good reason.
As much as I might hate their bloated scripting and dubious markup, it WORKS... out of box, as is, no screwball tweaks needed. If I need it bigger the browser textarea resize works, and it doesn't mangle bbcode if you don't like the editor.
EVERY other forum software out there now seems to second-guess you when you try to post code. It's such a royal PITA and it's one of the MANY reasons I go with SMF.
I had reasons for choosing SMF over vBull, Xenforo, phpBB, myBB, etc, etc, etc. Some are not readily apparent until you start actually trying to make posts with it.
Even when I do screw with it, I try to preserve what they did behind the scenes.