On my Emacs 27 on MacOS ("GNU Emacs 27.2 (build 1, x86_64-apple-darwin19.6.0, NS appkit-1894.60 Version 10.15.7 (Build 19H1030))
of 2021-05-17") I use ETBembo 18pt as font for org-mode. However Greek text in org-mode appears to use the font
mac-ct:-*-Helvetica Neue-thin-normal-normal-*-18-*-*-*-p-0-iso10646-1 (#x42C) which I find too thin. I suppose this font is chosen because ETBembo doesn't have Greek. However, I wonder why 'Helvetica Neu thin' is chosen.
If I copy/paste the text in a normal Emacs buffer (where Monaco 13pt is the default font) the Greek text uses
mac-ct:-*-Helvetica-normal-normal-normal-*-13-*-*-*-p-0-iso10646-1 (#x464), i.e. a normal Helvetica, which I find much better.
Does anyone know why the 'Helvetica Neu thin' was chosen in the first case and how to overrule this?