Quoting Stephen Winnall <stephen.winnall@...1452...>:
I looked around for anything to do with antialiasing, but I couldn't find anything which was obvious to me.
There's surprisingly little written on the issue I had in mind... It's not something with your document, though -- basically just a shortcoming of a common technique used by many renderers (simulating partial pixel coverage via the alpha channel).
The workaround is to combine the shapes or overlap them (when possible).
I am an SVG newbie though. Is it likely that Mac OS X was doing something?
Pretty unlikely... most of those apps have their own renderers rather than relying on OS facilities.
Any chance you could post the version of the document with the hairline (or even just a simplified document that shows the problem) so I could examine it to confirm my theory?
-mental