I feel like this is a really stupid question but my Opera browser (46.0.2597.57) on Arch (Antergos) doesn't display all UTF-8 characters. I guess it never did that but now that I need some of them (like Korean or Punjabi) I really noticed. All I can find is that I should use the drop down menu, "view" and then change the encoding. But it's just not there and I didn't find anything else in the settings.
Hopefully there is an easy answer to this problem because it just doesn't seem that big (I know of course that encoding isn't that easy in many ways...)
What font? As most fonts only include a small subset of Unicode, it is not surprising if any particular font is missing some character or other. Opera 12 would change fonts automatically (sometimes resulting in mismatched typefaces) but I'm pretty sure Blink doesn't do that.