@Azel ?
So I did actually go through Tarrangar's old posts on SB. I just skipped over every single thread I'd never heard of (which was 99% of them) and I quickly found this:
Now I distinctly remember having a discussion about the dangers of excessive immortality among the rich in the thread a while back. My position drew heavily on Piketty's statistics to justify the need for some sort of progressive taxation and for some means of limitation of the concentration of capital among the 1%. Tarrangar seemed quite unconvinced of the problem, disagreed with the morality of my proposal, and also disagreed with my socioeconomic points.
So!
Either Tarrangar read some of my arguments and sort-of remembered them (they're not 100% identical/understood, but his general ideas do seem to have shifted) or they had a wholly unrelated change of heart in the interim and I'm very disappointed.