I see the posted quote of the PM, but those can easily be forged. I don't know that there's enough evidence that would convince me to paint nixon99 red.
Your suspicion is not wrong, PM message could be edit. But I don't think xtraelv edited it. Since nixon99 self admitted that is bought account so red tag is appropriate in my opinions. Since your question is about legitimate of accusation it could be verify by moderators. If nixon98 had not sent PM to xtraelv then he can come on this thread with his statement. So he can report PM to any specific moderators to verify legitimate. Red tag could be removed if he able to provide valid evidence.
My opinion is nixon98 (current holder) bought this account. And that account has been hacked. So I have tag him, I will remove feedback if he come here and provide evidence. If it's true that he bought this account then I am not going to remove feedback.
nixon98 forwarded the conversation to me when I requested to see a copy of the PM after I saw their accusation from October 2017
Type mistake, Got it now. I have edited post. However, if nixon99 isn't bought account then he can come here and defend with evidence. And nixon98 could report the PM since both account is active. So problem could be solve.