I thought the trailing-off title was some sort of clickbait (which would be weird for Chen!); but actually the title is "Yes, the 8086 wanted to be mechanically translatable from the 8080, but why not add the ability to indirect through AX, CX and DX?", and I guess it just got asemantically chopped on HN's end. (To avoid my own clickbait, the one-sentence answer from the article, on which of course the rest of the article elaborates, is "Basically, because there was no room.")