This might do what you want just in a different way. (This I did in 1.8) You could give everyone a book with a command. This could /tp them to a room.
Under the floor of the room hide these commands connected to a clock of your choice(I used a hopper clock).
/testfor @p[r=10] This will test for a player within a radius of 10. If a player is within the radius a comparator will activate this command.
/give @p minecraft:writable_book
Have them write what they want to report in their book and place it in a trapped chest, connected to a hopper that places the item in a larger chest. Then have them push a button to report. .The report button should have 2 command blocks hidden behind it, one that clones the chest under the hopper to another room, and another that tells the player the report was sent
/say @p Report Filed. This is optional, but if you wanted to you could have a tellraw command that tells the owner of the world when someone is reported.
/tellraw (name) Someone has been reported it would look something like this:
.You could then go to the room where the chest was cloned and read the reports, but you would have to kick or suspend the players yourself.
This is a site with a book command generator: