Windows/Mozilla Firefox Quantum 59.0.2 (x64). The placeholder has opacity.
Solution:
::-moz-placeholder{opacity:1}
Normalize for all browsers (_probably unnecessary_)
::-webkit-input-placeholder{opacity:1}
::-moz-placeholder{opacity:1}
:-ms-input-placeholder{opacity:1}
Instead of normalizing Firefox, Webkit normalization should be returned.
It was removed due to a bug in Edge, but this bug was fixed in Edge 15.
Old versions of Edge lower than 15 have very low usage statics: 0.12% total
An up-to-date look at UA styles for placeholder text:
https://github.com/whatwg/html/issues/2561#issuecomment-569920124
Revert #603 maybe?
Most helpful comment
Instead of normalizing Firefox, Webkit normalization should be returned.
It was removed due to a bug in Edge, but this bug was fixed in Edge 15.
Old versions of Edge lower than 15 have very low usage statics: 0.12% total