Yeah, MoR and the lesswrong stuff is/was kind of a raging tire fire from what I noticed. Community definitely didn't live up to the conceit, at least, and got stuck in with some pretty rancid shit, though I forget details at the moment. Been years since I registered that mess as anything other than "avoid" in my mind.
I think I read most of the fic at some point, at least, but never actually finished... interesting enough concept but the execution just got progressively worse, iirc. It's been a while and I don't expect to reread it, heh.
Occasionally run into "rational" fics of one sort or another, but I honestly can't recall any really standing out as particularly notable, right now. Folks certainly try and it's not an outright deal killer of a proposition, in any case. I'll give the stuff a shot, if not actively seek it out.
E: ... anyway, TMNT thing has been read. Was neat... ish? Weird in places, like the part raph just straight up shot a dude in the head, or the part where donnie turned around and revived said dude while, uh, reprogramming their brain to be a good cyborg catboy instead of an evil one so they could collaborate to nuke an oncoming world killer asteroid. It, um. Was a thing.
Definite upside, though, raph totally did punch hitler right in the face, so hey. also hitler's brain (just the brain, in a jar, with robot limbs) was running around trying to kill people but. look, it was odd, alright. Just take your mutant turtles punching nazis and be happy with that.
Also raph's girlfriend or whatever apparently wasn't the major TMNT fox chick, but a... different one? Really similar character design, but not the same one, it seems. Eh.