Marelli
It's suddenly not so perfect anymore when some other player disagrees with something you say, and calls in 10 of his buddies to all flag you as a troll.
I sure understand this concern; there is a risk of wrongful flagging. However, everything would be logged for CSRs to review, and any wrongful flagging would be punishable. Everyone would think twice before misusing such feature for their personal feuds. Who would risk, say, a day of ban, just to make someone silent for a hour?
The moderation mechanic itself is up to discussion - but there surely is a room for some kind of moderation, whether semi-manual as I suggested, or completely automatic (filter-based). We wouldn't want new players being greeted by the avalanche of "f*cks" and "b*tches" all over the /universe chat, would we? It doesn't make a good first impression.