I'm a little uncertain about mutual merits that are for one merit point per perit instance given. Why I say that is because I've read threads where an issue has been discussed and persons with green trust have given each other merits for posts. You'd have to go back and read through their mutual merits and see if they were for Shit Posts TM or not. (same goes for trust wall posts)
Yes, I'm not sure if it's enough evidence to give fakegurutu a red tag for Merit trading and theymos said once it's only safe to tag them if there is a strong evidence. Shasan found out that the Merit transfer was done only in 7 minutes: https://bitcointalk.org/index.php?topic=5102614.msg49438635#msg49438635
fakegurutu sent 3 merit to sham100899 at 6/6/2018 4:29:58 AM and sham100899 sent 2 merit to fakegurutu 6/6/2018 4:36:41 AM That means merit exchanged only within 7 merits. Both are using the same platform of bitcoin wallet. sham100899 and fakegurutu
Of course, he could have given the Merits for the best post to avoid meriting ShitPosts, but looks like a red tag is only deserved yet for sham100899, hisori (hard proof: enrolling multiple account in the same bounty), and not enough proof to tag fakegurutu for Merit trading and being an alt of the other ones. Or how would you decide?