I've actually experienced that nearly all posters of a locked and hidden thread return to go through it again (Unless they are so upset that they don't come back at all).
Instead I think it's a bit of a generalization to assume flags are an issue that appeared mostly because it's being talked and complained about so much in recent times, as well as the fact that being flagged, even if it happens just once, can be really annoying and/or shocking for a user.
Part of it may be my fault for addressing the complaints (as I am doing here, causing a thread to derail - sorry OP), but I always feel like sharing background information on how things actually work helps avoid confusion in the future.