Telling someone that you're going to report them should be a punishable offense. It is used too often by trolls to instigate a fight or a flame war in all chat. The rest of the team doesn't care. The other team REALLY doesn't care.
Asking the other team to report someone should also be a punishable offense. Again, it is used to start flame wars and trolling. In many cases the enemy doesn't care about what you guys are arguing about.
If somebody is breaking the summoners code then report them. You aren't helping anybody by making them rage harder/ troll harder/ feed harder/ verbally argue with you. Well, you might be helping the enemy team by fighting among yourselves.
The reporting function is too often used as a threat or a form of verbal abuse in order to instigate rage or further trolling. You do not need to voice your intent to report somebody in order to report them.