The definition of the word LEST is "for fear that" or "so as to prevent any possibility that". So do the phrase "for fear that we forget" or "so as to prevent any possibility that we forget". Both make sense as to what they are saying. They are showing pictures of twin towers so as to prevent any possibility that we forget.

The definition of LESS is "Not as great in amount or quantity" or "Lower in importance, esteem, or rank". So do the phrase "not as great in amount or quantity we forget" or "Lower in importance, esteem, or rank we forget". That doesn't make sense or match what they are trying to convey.

I think people have heard the phrase, didn't know what it was, and thought they were saying less we forget and have then incorrectly written the phrase that way.

Dave.
SS - 1029