PB&M specialists calling other players liars
In the linked thread, a poster linked to their match history and pointed out that a player, a mid heimerdinger, intentionally fed. After pulling up the replay from the player's match history, it was obvious that the player mentioned in the OP intentionally fed at least two kills to the midlaner - running directly into turret range in the first couple minutes of the game, and making no attempt to leave turret range or dodge incoming attacks from the enemy laner. They died a couple of other times in more ambiguous fashion, but given that they are diamond rank, those deaths are also very questionable.
Leaving aside all discussion of the game's intentional feeding detection or Riot's inaction, I have no idea what the expected behavior and qualifications of a "specialist" are, but I don't think this meets those standards:
6 deaths in 12 minutes is hardly "running it down mid". Did he grief/troll? Maybe. I don't care to find and watch the replay. But don't lie about what he did.
He got stomped in lane, then y'all gave up.
If he "didn't care to find and watch the replay", then he should have kept his commentary on how much of a liar the OP is to himself.
Rujitra owes this player an apology, and judging by some of the other comments on this part of the boards, owes his blue tag back to someone who doesn't break the first two rules of the player behavior board (namely "respect each other" and "be helpful") on the regular.
On a related note, I reached out on the boards discord about this matter, and never received a response after pinging @Moderator like the message in that channel requires. I saw that I had a ping from that server, but upon clicking into the server again, the message was deleted and I never saw what it was.