Because the Great Mod in the sky is THE Great Mod that will tolerate no others before him.

He can do what he likes. His universe! You are privileged to drink from his cup!

I often cannot find my posts later by simply looking at the main blog. To see them you must sometimes go to "my posts." I suspect that Admin has a reason for this and what is most relevant might be it.

I haven't noticed posts being moved around in the general forms but I can speculate that it's being done to posts that are either trending or not trending... As for your posts being removed, only you can figure that out... Do you get an email notification from admin when your post is removed? If not, then a mod removed the post from a member hosted group...