I did not get it to work.
I made the change in the theme files directly, the only change being the font weight from 300 to 600. It does not seem to make any difference. I tried it at 900 as well.
Although my intention is to bold the titles, I tested it with an H1 inside the post also, just to see if it works. Still, no difference. Of course I can bold the H1 text inside the post if I choose to, but I have no way to bold the title in the editor. Is there anything else I can try? I changed the weight back to 300 for now.
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