"Your eye spends non-zero amount of energy to scan, parse and join multiple characters into a single logical one."
citation needed
citation needed
For example, the == and === look quite a bit similar in the font. You have to compare relative sizes, whereas with the normal fonts you can count the spaces.
The rest of the ligatures look pretty cool!
Regarding the difference between == and ===, latter has three lines (and so does !==), so in fact in Fira Code === and !== the looks implies the meaning, whether in other cases you have to bend your mind to accept that negation of “three equals” is a “two equals and a bang”