As an additional note, it seems firefox is also partially affected. Once doing the steps to reproduce, if firefox is open, the render on some pages get completely screwed up.
I don't think the issue is with fontconfig itself, but some programs using fontconfig in a way that is not supported (there is an API, but at least in OpenOffice, it access a direct pointer which becomes void if a font is adding or removed).
I can confirm this bug.
Steps to reproduce added to the summary.
As an additional note, it seems firefox is also partially affected. Once doing the steps to reproduce, if firefox is open, the render on some pages get completely screwed up.
I don't think the issue is with fontconfig itself, but some programs using fontconfig in a way that is not supported (there is an API, but at least in OpenOffice, it access a direct pointer which becomes void if a font is adding or removed).