The author looks to be Japanese, so that's probably why.
In Japan, grade school teachers often use the symbols like so:
○ = correct × = incorrect △ = partially incorrect
I'd prefer the yes, no, partial though as well.
Re:Show HN: A fast JSON library for Go
by kevincox on Tuesday February 09, 2021 @08:09AM
(#26077035)
Ah, thanks for explaining that.
However yes, for an English README it probably makes sense to stick to words to clear any confusion.
I fixed it ! Thanks !
My first thought was "yes", "no" and "ish" since the last one is a similar length to the first two.
My second thought was that that was probably just going to move the confusion to non-native english speakers.
Given a math background, ~~ for 'ish' is also tempting ... but while writing this out I've circled back around to "I can't think of anything better than partial".
I would suggest using words like "yes", "no" and "partial". They are short and clear. If you really want to do symbols I recommend using for yes, and still spelling out whatever triangle is supposed to mean.