Having users reply to the message for appeal is what allows the exploit to succeed. Changing the appeal process to an email or some other method would reduce this attack.
Edit: perhaps a button you click to open an appeal window.
I looked it up to give a more clear answer:
The term 5X5 is rooted in the communications within military forces through WWII to mean "I understand you perfectly." The first number represented the Signal Strength of a radio communication, and the second number represented the signal clarity on a scale from 1-5 -- 1 being the worst; 5 being the best.
AngelCole is correct. Here is an Aussie nurse confirming that's exactly what is happening.
https://communities.win/c/GreatAwakening/p/13zMnScNIG/beachmilk-aussie-nurse-confirms-/c/
It is an exploit in the sense they are using the format of the appeal process to keep users from interacting with actual mods when trying to appeal the fake ban. If they don't try and test the system by making another post, the scam succeeds.
I realize this might still work even if the appeal process is changed, but it has a much smaller chance.