Good use of verification code:
1. Send player a /tell, if player is busy try contact him in Say, Yell, Shout mode
2. Player should warning other player about sending verification code before do it
3. Follow player for at least for 2 minutes.
4. if player received a /tell with RMT spam, he's allowed send verification code
5. Send him a informal verification code. Example: "Cecil, can you type P0T4T0 to verify if you are a bot or not, please?" wait at least 5 minutes for an answer

I dont know how GM investigate but if you receive a report due to bad verification code:
1. verify if player send /tell before
2. player who are mining, harvesting and killing things should answer /tell
3. players who are human and ignore /tell from players are unable to report
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Well... any ideias? if people make a good use about this tool, maybe it will help A LOT GM team and STF to banish RMT

PS: Sorry for the bad english.