Can the blocks of code on StackExchange posts ({} icon the toolbar) be reduced or increased in size by changing the font size, or any other means?
Through a userscript, you can:
// ==UserScript==
// @name Stack Exchange Code Formatting CSS
// @include http://*.stackexchange.com/*
// @include http://*.stackoverflow.com/*
// @include http://*.serverfault.com/*
// @include http://*.superuser.com/*
// @grant GM_addStyle
// ==/UserScript==
GM_addStyle ( "code,pre { font-size:14px !important; white-space:pre-wrap }");
The default font size is 13px. Applying the font-size to code is what works. In my example, I wanted to word-wrap the (pre) text so I made it simpler by applying the two properties to both.