Gravedigging?

Ok I will post exactly what happened:


I went to this guys thread who was showing everybody in detailed explanation how to execute/perform a kickflip on a skateboard.

I thereby post something along the lines of "I've been skateboarding for 5 years and I still can't land a kickflip lol" , and i recieve the infraction of gravedigging.

I would simply like to know why i recieved this infraction, and what gravedigging is.

Any advice is helpful >_<

 

The thread was 3 months old.

And, it's already expired.