From Who decided saints have halos?
The halo thing is actually pretty intricate. There are not only plain round halos, used to signify saints, there’s also the cross within a halo, used for Christ; the triangular halo, used for representations of the Trinity; and the square halo, used to depict unusually saintly living personages, such as certain scandalously underpaid journalists I could name. (Square haloes, I am obliged to report, look totally Polish. No offense.) Occasionally you also see things like the hexagonal halo, about which the less said the better.
A quick google search of “hexagonal halo” turned up this
Here is a very rare hexagonal halo that surrounds the head of Hope one of the three virtues. This halo distinguishes the wearer from ordinary heavenly beings, who have circular halos, and from earthly beings who wear square halos if they wear any at all. This halo seems to set her apart as a person representing an idea or value.
At first I was thinking, with the hexagon and all, it had to something satanic (a Judas halo or similar). But that doesn’t appear to be the case. Cecil never really says in the article. So why “the less said the better?”
“The less said the better” is a throw-away line.
It is meant to be humorous. Such as in a Monty Python sketch when they say “Say no more.” “Know what I mean?”