To assess penalties means to warn someone (teasingly) about the person they are dating/tricking with/about to get into a relationship with. A variety of sports-based metaphors are used. Farcically, they've been somewhat mixed and mangled, much to the bemusement of the few #gaysfers who actually know anything about sports (hi RainKing, M13, bjjoe, et al!).
In volleyball, a yellow card is displayed by an official as a warning to a player or coach. If the official displays a red card, it indicates a severe penalty -- usually resulting in a disqualification. On channel, to give someone a yellow card means to warn them that the person they're about to do (whatever) with is kinda sketchy. If you give someone a red card, you're strongly disapproving and it usually implies that you have some relevant personal experience to share with them.
The follow-up to red card is usually something along the lines of game misconduct plus $300 fine or three-game suspension -- which are borrowed (liberally) from the sport of hockey. On channel, these are used to mean a hopelessly irreconcilable relationship; particularly if the people involved are breaking up or euphemistically "taking some time apart".
To wave off a player (e.g. as in basketball, soccer, etc) means to call for a substitution or a player switch. It's usually done by a coach to rotate new players into the game. On channel, it means to warn someone off of either someone or some topic. It can be used like "don't go there..."