When the font-family property hasn't been specified in the FO file, it defaults to "sans-serif,Symbol,ZapfDingbats". But the latter two aren't available in a bold variant. When a block of text can be rendered using the sans-serif family only, warnings are still issued about unavailable Symbol bold and ZapfDingbats bold. This is likely to puzzle users. Strangely enough, no warning is issued when font-weight is set to normal and font-style to italic, although Symbol and ZapfDingbats aren't available in italic version either.
Created attachment 23723 [details] Sample FO file showing the problem
resetting P2 open bugs to P3 pending further review