That is normally down to engines then
Blogs are the worst for that.
You can bang out blog submissions all day long. A lot will have a comment box, but the comments never get approved
You need to check your submissions stats and compare the submitted against verified on the engines you use
When I hit my first daily 200,000 submissions, I then went through and drop the high submission low verified engines
Also look at the content your using. If its out the box ser comments etc, you will be moderated and no doubt your comments will be deleted