"Why can't I vote on stuff?"
Have you unlocked the "Voting Member" rank/ability? If not, then this is why. You also can't vote on your own content (exercises or results that belong to you), you can't vote on something you've already voted on, you can't vote on an exercise without completing it at least once, and you can only vote on results when actually looking at them.
"My stuff is getting downvoted?"
If it is results, did you shoot the course of fire correctly? Did you do really poorly? Do you have a Hillary 2016 poster in the background of your targets that folks can see?
If it is an exercise, does it work and make sense? Is the preview information accurate? ... not just to you, but Joe Schmo who is downloading it and doesn't know you. Try looking over your exercise or having someone else take a look and see if there is something you can improve.
"How and when should I vote/report?"
This is up to you. On exercises, as long as it is well structured, adequately explained, and runs correctly, it's probably worthy of an upvote. If it could use some work, then maybe just don't vote on it. If it is broken or difficult to understand and use, then a downvote and report may be in order.
Similarly, on results, as long as it looks like the person shot the exercise per the instructions and gave it an honest go with decent results, it's probably worth an upvote. If he/she shot it correctly but didn't do so hot, then no vote is a good idea. If they jacked around and didn't follow instructions, then you might want to downvote and report it.
"Do others see when and how I voted/reported?"
No, it is anonymous.
"Can I change my vote?"
Not yet. We're working on it.
"Does reporting effect shooter points?"
No. If it is not in the list of things on the "My Ranking" page that affect your points, then it doesn't affect your points.
"Why can't I report stuff?"
Have you unlocked the "Community Watch" rank/ability? If not, then this is why. You can only report exercises from their details page, or your results on that exercise, and you can only report results when looking at them. Please keep in mind that excessive or abusive reporting will likely bring punitive action against you.