This is not true in every instance, because a lot of these scammers has caught on to the fact that short discussions are scrutinized more often and easily identified, so they are writing more detailed threads lately
![Tongue](https://bitcointalk.org/Smileys/default/tongue.gif)
You might have to change that statement a little and probably say, "The OP is mostly very short".
![Roll Eyes](https://bitcointalk.org/Smileys/default/rolleyes.gif)
![Roll Eyes](https://bitcointalk.org/Smileys/default/rolleyes.gif)
I'm not claiming that any of the red flags that I've posted is enough to call someone a spammer, even all of them at once don't necessarily mean that it's a spam, those are just things that should raise your suspicion. You're right that spammers can have longer posts, and you are right about poor grammar, I even considered adding grammar as another red flag, but decided against it, because there's a lot of non-native speakers on this forum, so it's not a strong reason for suspicion.