I collected and tested discussed solutions:
Windows10 Prof x64:
* FireFox v.56.0 x32
* Opera v.49.0
* Google Chrome v.61.0.3163.100 x64-bit
macOs X Serra v.10.12.6 Mac mini (Mid 2010):
* Safari v.10.1.2(12603.3.8)
* FireFox v.57.0 Quantum
* Opera v49.0
Semi (still micro fat in Safari) solved fatty fonts:
text-transform: none; // mac ff fix
-webkit-font-smoothing: antialiased; // safari mac nicer
-moz-osx-font-smoothing: grayscale; // fix fatty ff on mac
Have no visual effect
line-height: 1;
text-rendering: optimizeLegibility;
speak: none;
font-style: normal;
font-variant: normal;
Wrong visual effect:
-webkit-font-smoothing: subpixel-antialiased !important; //more fatty in safari
text-rendering: geometricPrecision !important; //more fatty in safari
do not forget to set !important when testing or be sure that your style is not overridden