AR 600-37 covers letters of reprimand and you are allowed to appeal them. If you received another LOR just for appealing this may be retribution and something that JAG needs to be informed of, or at least the next higher Commander.
A number of issues concern me here.
First, a Soldier must be given the opportunity to rebut any letter of reprimand. Second, the letter of reprimand must be based on evidence, not just the word of someone: i.e., supporting documentation must be given to the Soldier being reprimanded. That can be a sworn statement, Commander inquiry investigation, etc. A reprimand cannot be given because a Platoon Sergeant verbally told a Company Commander they saw a Soldier smoking where they should not be.