I think it attaches both usernames - the member reporting it and the member who is getting reported, although how the staff know who is reporting and who is being reported, don't ask me that one cause i'll probably get it wrong

thats something admin probably can answer (if its not a admin secret so shh willowtigger before you get yelled at by admin for mentioning admin secrets)

for the record: willowtigger does not know any admin secrets, please dont do anything to her for being suspected of knowing any cause she does not know any