What does the exclamation mark on a timestamp mean?

I've noticed a couple of times that in comments (where I've seen it, but maybe it's in questions/answers as well) that sometimes the stamp is -- UserName X [time unit(s)] ago !

Where most other comments are -- UserName X [time unit(s)] ago

What's the exclamation point mean?

• Does it look like this? – C. Ross Dec 19 '10 at 2:39
• @C.Ross Yes it does! – Pulsehead Dec 19 '10 at 14:10

Actually, you're probably referring to the edit indicator, which looks like a pencil. If you hover over it it will say this comment was edited. If it's been edited multiple times it will also state that.