I'm sending this on behalf of my coworker Sharon Correll:
We've run into this dotted circle problem on our ScriptSource website (scriptsource.org) where we are trying to display diacritics from many scripts in isolation, using a wide variety of fonts, eg: http://scriptsource.org/block/0980. I wrote a blog post about the problem: http://scriptsource.org/entry/vr82t8n6pt We've seen single dotted circles, double dotted circles, no dotted circles, and even no diacritics at all. There is very little consistency, so it seems like some interaction between the font-smarts/rendering-engine/browser. I didn't investigate deeply enough to figure out which, but bottom line, there doesn't seem to be a good across-the-board solution. Solving it on a script-by-script basis is not ideal, but we might bite the bullet and do that if we could figure out something that would actually give reasonable results. Sharon Correll SIL International
