Strum Direction Consistency

I really need to ask this, but am not sure if it's relevant to all styles of playing or just noter/drone. I'm currently stopping lessons as of tomorrow. May return later, but something is bothering me: strum

direction. There are tons of discussions here on in or out. I prefer out which stresses the melody for Ionian tuning. I can understand that is then best to keep consistently for the downbeat (something I sometimes have trouble identifying). Maybe it's just a thing for MD, but does the earth cave in if I stay on beat and hit the correct note, but accidentally go the wrong direction with my strum? Yes, the stress or emphasis may be slightly off, but how serious a musical mistake are we talking here?