I agree that the multiple definitions are confusing, but I'm not sure that you consistently employ the "believing in truth" version in your post above.* It's not "believing in truth" that gets people into prisoners' dilemmas; it's trying to win.

*And if you did, I suspect you'd be responding to a point that Eliezer wasn't making, given that he's been pretty clear on his favored definition being the "winning" one. But I could easily be the one confused on that. ;)

"In that case, believing in truth is often non-rational."

Fair enough. Though I wonder whether, in most of the instances where that seems to be true, it's true for second-best reasons. (That is, if we were "better" in other (potentially modifiable) ways, the truth wouldn't be so harmful.)