I mean even if no-one else interacted with the post and you brought it up, it might still make him defensive. Some of these terminal lefties treat Reddit like their personal diary and knowing the "enemy" has been rifling through their diary would probably put some of them in fight or flight before they even recognize the helping hand being offered. If he's along for Charlie's death, he's almost definitely going to consider you an enemy still.

Plus at this point, after you've already text him to check in, any fresh engagement on that post would be super weird if he isn't retarded. Which, y'know, he might be, but in which case you can probably do better than that in a bro.

He ruined your friendship, he ruined his life, at this point the only thing he seems capable of doing is ruining your day/week/month too if you let him. Entropy rolls ever onwards and some things are just lost forever. But new things are unveiled too, like not needy, disloyal trainwrecks for friends. Look around and offer them your friendship instead. At the very least stick to one who understands bros before hoes better.