> "Strictly speaking, I would classify this as user error, not a browser flaw, though it's an easy mistake to make"

I agree, but browsers should use console warnings to report when they resort to font synthesis or weight substitution. That would go a long way to help web developers understand this problem.

Similarly, console warnings to report character substitution when a needed character is not present in the font-family list would be useful.

In general, I want more transparency from text rendering engines when they encounter something that may not be what a professional designer or typesetter would want. The opacity of today's engines breeds ignorance among their users (web developers).