The בית חדש in O.C. 168 writes the following:
אלא דלהלכה ודאי במידי דתליא בגירסאות אזלינן לחומרא הכי והכי
In something which is dependent on variant texts we are stringent in both directions.
I have never seen this rule before, and מלתא דלא רמיא עליה דאינש לאו אדעתיה (that which you aren't looking for you don't notice) but I have the sense that in my experience learning halacha this rule is not generally followed.
Do any other poskim follow this rule, and is it sourced somewhere?