Well, I won't edit it but I'll add some stuff.
It only takes one report to flag a match for review, so getting more can't make it check a match any harder. Multiple reports may result in triggering a review faster, but they won't result in a harsher or false punishment; the player still has to exceed a threshold of confirmed negative behavior in a large number of these reported matches. Premade groups only have the power of a single solo report as well, so there's no abuse from premades with reports as well.
Triggering a review (not a punishment) based on report volume is a good thing. If 30 individual players decide on their own to report someone across only 5 games, chances are something is up and the system should check it out; if a player is reported 30 times evenly across 300 games, they are probably causing much less harm and wouldn't likely be reviewed. Trying to manipulate this is not good for the system and tends to cause drama of its own (being threatened with mass reports tends to upset players and distract from the match) so should be discouraged. Players can decide on their own what they want to report.