How many times should a comment be marked as noise/spam before it is deleted from the site?
In these questions, it is always about balance.
There are three prototypical cases, with much gray area in between:
Obviously, we want heinous spam to go away quickly so it bothers the lowest number of people. We also want the angelic comment to remain, because on the internet, there will always be childish adults who just want to be disruptive.
Based on [Angelic] it should be infinitely high, and based on [Heinous] it should be zero. If we add, then take the average it comes out to half-infinity, or "about six".
Six is actually a good figure, because it usually means that one or two people cannot gang up and purge someone else' comment, it is unlikely that a comment could receive six flags accidentally or without any sort of wrong doing, and it also will not take an unreasonably large amount of time for an unwanted comment to be flagged into oblivion.