Just to clear some things up, I don't receive any pm's when you use the report button (me being a local mod). Only smod's and higher ups receive reports, I'm not familiar with the report system, but I'm pretty sure smod's don't receive pm's when you report something. If you want to know more about this you will have to wait for somebody who knows more about this to answer you.
About the reporting the useless posts question, of course you can report useless posts. Reporting any kind of rule breaking can only help moderators to moderate the forums more easily. Don't get intimidated by the description of the report button, I do my own share of reporting useless posts in other boards, but you have to be aware there's a line between reporting useless posts and spamming the report option with the post you personally dislike or disagree with.
Reporting posts that don't break the rules can result in infractions.
I hope this clear things up.
If you have any other questions, ask away