Signature Format

[Tempus]

I'd personally separate sigs from the main post with a single horizontal rule. Although that could be confusing if someone uses a hr in their post. Maybe - if it can be done painlessly and prettifully - the sig section at the bottom could have a subtly darker background colour. One forum I'm on separates post content and sigs with two dashes (like this: --) and I can't recall having any difficultly distinguishing between the two.

Here's a mock up I did demonstrating what I meant by the background colour suggestion (click for non-blurry, full res image):