My guess is the titles get auto adjusted by Hacker News, but the script that does it doesn’t have logic for a trillion and only goes up to a billion, hence the weirdness of a string match and replace
Billion is a word for a large number, and it has two distinct definitions:
1,000,000,000, i.e. one thousand million, or 10^9 (ten to the ninth power), as defined on the short scale. This is now the most common sense of the word in all varieties of English; it has long been established in American English and has since become common in Britain and other English-speaking countries as well.
1,000,000,000,000, i.e. one million million, or 10^12 (ten to the twelfth power), as defined on the long scale. This number is the historical sense of the word and remains the established sense of the word in other European languages. Though displaced by the short scale definition relatively early in US English, it remained the most common sense of the word in Britain until the 1950s and still remains in occasional use there.
There are times where diverting from normal conventions make sense. The average consumer might not know that 1Gb/s is faster than 750Mb/s. That being said, I don't think I've ever seen anything along the lines of 1G,000b/s.