The problem is this sites css stylesheet

href="/styles/common.css?v=7.5.6"

Code tags are rendered using inadequate css rules.
Moderating/editing a post is the wrong solution.

The cheapest right solution is to add one of the following to common.css , should work on all modern browsers

Code:
.ubbcode-block {
	max-width: 400px;
}

Code:
.ubbcode-pre pre , .ubbcode-pre {
	font-family: monospace;
	white-space: pre-wrap;
}

Code:
.ubbcode-pre {
	font-family: monospace;
}
pre {
	margin: 0px;
	white-space: pre-wrap;
}


For which browsers support pre-wrap see
http://www.quirksmode.org/css/whitespace.html