Sirocco provided a link to this thread explaing about the public
warning system:

http://forum.rscnet.org/showthread.php?t=35566&highlight=public+warning

but in less than a day this thread was removed.

Basically, the thread mentioned that some older members were getting
preferential treatment over newer members, and that the yellow/red
card warning system was silly.

A moderator responded that they once used private warnings, but users
were ignoring those, so they went to a public warning system.

This appears to be an outright lie. If a user was ignoring warnings,
that implies the user continued his bad behavior and received more
warnings, which would have caused him to be banned.

No other racing sim forum uses a public warning system, so it's apparent
the problem is with RSC's moderators and not it's members.