Similar to what Brad says, posts not in line with EA mainstream, or just exploring or giving ideas, or not written in EA-style, or drafty are often down-voted very early on without engaging in discussion or giving any reason for the down-vote.
Even though forum moderators try to engage people to write even if the post is not perfectly polished or thought through—most people are very busy!-- to incentivize exchange of ideas, the dynamics of the forum make it basically useless as such posts are usually very quickly hidden. It often feels useless to write anything.
Another reason, which is understandable and difficult to avoid, but that I find a bit surprising in this forum, is the status and political dynamics: I’ve seen several times good posts with very low karma and afterwards very similar posts written by known EAs that have lots of karma.
Sure, that was not meant as a reproach!