Some of my posts have been deleted by moderators, but I'm still fine until now. However there are some differences that I noticed, when I was a newbie, my short posts were more easily deleted by moderators but once I had a higher ranking, my short posts were fine. I don't know why that is
Unless I'm wrong, if not, I don't see post length as what's being used to determine whether a post should be deleted or not. You can write a 1-line post that stays on topic with the thread and has a valid message that it's passing to the people, and it won't be deleted, but if the comment appears to be just some form of exclamation and nothing too serious to be located in it, then it can be wiped out by moderators as it appears to be a scam.
Even lengthy posts get deleted; if they're not organic and look like shit to a thread, I think they will also still get nuked down unless there are some exceptions to how posts are considered based on rank, which I have not read about yet.