E-Cred is a reputation system that is displayed next to your avatar. Anyone can give you +1 E-Cred by clicking the Applaud link. They can also take away 1 point by clicking the Boo link.
If you see someone reply with the number sign (#) that is short hand for I gave you +1 E-Cred. We also have a smiley now that means the same thing:
We have one for boo too, but people don't always use it for that. In fact it is very rare for someone to get a real E-Cred boo in here. Here is the Boo smiley though: