@shackleton – generally it’s OK. I’ve had rides flagged and have flagged rides/segments myself but in all cases it’s been for genuine reasons.
On the ride I had flagged I was contacted by Strava: “Can you check activity x?” When I looked at the data everything was normal until the last seven or eight Km when I appeared to have ridden at a constant 32kmh uphill, downhill and along the flat! Everything else was fine. I just trimmed the end of the ride.
Similarly when I’ve flagged rides/segments it’s because it’s obviously been logged in a car: beating the local pro-riders on an 8min climb by 3mins as an example.
In any group of people there will be dicks, sad fact of life, Strava is no different.