Yes, everyone is encouraged to help, but we try to avoid putting spoilers in a thread that's not marked as a spoiler. The majority of the community prefers not to "stumble upon" spoilers in seemingly safe threads. Sometimes, when a spoiler is added to a thread that isn't marked, and others have already answered adequately (especially with a pointer to the spoilers thread in the Guide), I delete the spoiler post to avoid having to tag the entire thread as a spoiler. It's nothing personal, it's just preserving a longstanding tradition here.