General rule of thumb on the Internet is "You're not as witty, smart, and funny as you believe you are."
The REAL reason I see is that, if there's THAT much urge to talk about it, there wouldn't be a dead thread, now would there? And you can just start a new one and we'll all jump into that one.
Seems reasonable enough.
Current users may have said all they want to say on a topic, but what about new users? Often artists on here have a single thread where they post links or thumbnails to their latest work. Do you guys really want new users to start a new thread every time they want to say "Cool art, man!" or should they should be expected to refrain from commenting at all because their late to the party? Don't get me wrong, I think not reviving old threads is a useful guideline to have, but I just don't think it should be a hard rule that is arbitrarily enforced, especially on a small forum like this.