"Foreign bodies accidentally taken into the mouth with food (gravel, stones, bird shot) are removed with thumb and forefinger, as are fish bones and other tiny bones. If a gnat gets into a beverage or  some other unappetizing creature turns up in or on a diner's food, he fishes it out, unobserved (so others won't see it and be upset), and then either proceeds or leaves the drink or dish untouched, depending on the degree of odiousness of the intruder. A gnat or a tiny inchworm on lettuce shouldn't  bother anyone, but most fastidious people draw the line at a fly or worse.” (Amy Vanderbilt's Complete Book of Etiquette, 231)

Foreign notions accidentally taken into the mind with conversation are removed with…

If an uncomfortable thought gets into a narrative, or some other challenging concept turns up in a workshop paper...(so others won't see it and be upset)…and then either proceeds or leaves his conceptual world untouched, depending on the degree of odiousness…

Some scare quotes or an unusually long footnote shouldn’t bother anyone, but most fastidious people draw the line at…