That's a ban message. The feature has been there since the start of 8chan. How do you not know this?
Yes, the red text is a ban message. Moderators can optionally put a reason for a ban and it appears in bold red text at the bottom of the post. You must not have been to any of the other boards if you've never seen it. It's a basic site feature, nothing to get worked up about.
There's only one thing I want to do with my idle hands.
It's spelled aerial.